Fill in the blank with the most appropriate word to complete the sentence: The employee had become _____ to both the manager's praise as well as reprimand, indicating how the worker reacted to feedback.

Introduction / Context:
This is a vocabulary and usage question that asks you to choose the most suitable word to complete a sentence about a worker's reaction to praise and reprimand. The sentence describes how the employee responds to both positive and negative feedback from a manager. Such questions test not only your knowledge of word meanings but also your ability to sense which word fits the context and collocates naturally with the phrase had become and to both praise and reprimand. Understanding fine differences between similar adjectives is crucial for doing well in English usage sections in competitive exams.

Given Data / Assumptions:

• The sentence is: The employee had become _____ to both the manager's praise as well as reprimand.
• We must select a single adjective that logically and idiomatically completes the sentence.
• The options describe possible attitudes or emotional states: hardened, indifferent, hostile, immune, and sensitive.
• We assume the sentence describes a typical office situation where constant feedback has shaped the employee's reaction.

Concept / Approach:
The key to solving this question is understanding the phrase had become and how it combines with adjectives to express a gradual change in reaction. The sentence suggests that after repeated praise and reprimand, the employee no longer reacts strongly to either. The preposition to in the structure become adjective to something is also a clue. Expressions such as become immune to criticism and become indifferent to praise are common. The preferred answer must capture the idea of not being affected by either positive or negative comments, and it should sound natural when used with to and the pair praise and reprimand.

Step-by-Step Solution:
Step 1: Consider option a, hardened. Hardened to something can mean that a person has become less sensitive or more tough. However, this word often carries a slightly negative or harsh tone, frequently used with crime or suffering, such as a hardened criminal. It is possible but less precise here. Step 2: Consider option b, indifferent. Being indifferent to something means not caring about it. While this could fit in meaning, the sentence emphasises the idea of being unaffected by both praise and reprimand, which is closer to not being influenced, rather than simply not caring. Step 3: Consider option c, hostile. Hostile to something means openly unfriendly or aggressive toward it. This does not fit the context, because the sentence does not suggest that the employee aggressively opposes praise or reprimand. Step 4: Consider option d, immune. Immune to something means not affected or influenced by it, often used with phrases like immune to criticism or immune to flattery. This matches the idea that praise and reprimand no longer have any impact on the employee. Step 5: Consider option e, sensitive. Sensitive to something means reacting strongly to it, often emotionally. This is the opposite of what the sentence suggests, because the employee is described as no longer reacting strongly. Step 6: The adjective that best captures the idea of no longer being affected by either praise or reprimand and fits the collocation become immune to is immune. Therefore, option d is the correct answer.

Verification / Alternative Check:
A good way to verify is to test each adjective in a similar example. For instance, you can say After years of criticism, she became immune to harsh comments. This is a common and natural expression. You could also say He became indifferent to criticism, which suggests lack of interest, but immune emphasises not being influenced at all. In the given sentence, the employee faces two types of feedback, praise and reprimand, and yet reacts to neither, which is the classic context where immune to is used in English. Language corpora and common exam patterns frequently use immune to criticism and immune to flattery as standard collocations, confirming that immune is the best match here.

Why Other Options Are Wrong:
Option a, hardened, partly fits but usually implies becoming tough or callous, and is more often linked with suffering or crime rather than everyday office feedback.
Option b, indifferent, focuses on not caring rather than not being affected, and is less precise than immune for this particular context.
Option c, hostile, clearly conflicts with the sentence because there is no hint that the employee reacts aggressively to praise or reprimand.
Option e, sensitive, suggests strong emotional reaction to praise or reprimand, which is the opposite of the intended meaning of the sentence.

Common Pitfalls:
Learners often confuse indifferent and immune because both convey a lack of response. However, indifferent is about lack of interest, while immune is about lack of effect. Another pitfall is choosing hardened because it looks attractive and suggests emotional change, but it is not the most natural collocation with praise and reprimand in a workplace setting. In vocabulary questions, it is vital to pay attention to collocations, which are typical word combinations that native speakers use regularly. Knowing phrases such as immune to criticism or immune to ridicule provides a strong clue for this question.

Final Answer:
The most appropriate word to complete the sentence is immune, so option d is correct.