In the following question, out of the four alternatives, select the alternative which is the best one word substitute for the given phrase: Irritating inconvenience.

Introduction / Context:
One word substitution questions measure your ability to match concise vocabulary items with longer descriptive phrases. The phrase given here is irritating inconvenience, which refers to something that causes minor trouble, annoyance, or extra effort. It may not be a disaster, but it is bothersome and frustrating. Your task is to choose the word that best captures this idea in a single term.

Given Data / Assumptions:

• Phrase: Irritating inconvenience.
• The sense is of something annoying and troublesome, often involving unnecessary difficulty.
• Options: tranquillity, hassle, harmony, rectitude.
• Only one option is both semantically close and commonly used for such minor troubles.

Concept / Approach:
In modern English, the informal noun hassle is widely used to describe a situation or task that is annoying, inconvenient, or involves too much trouble. For example, standing in long queues can be a hassle. The word tranquillity means calmness and peace, which is the opposite of irritation. Harmony refers to agreement and pleasant arrangement, not inconvenience. Rectitude refers to moral correctness. Thus, hassle is the only word matching the meaning of an irritating inconvenience.

Step-by-Step Solution:
Step 1: Interpret irritating inconvenience as something that causes unnecessary trouble or annoyance. Step 2: Check the meaning of hassle: a situation that causes a lot of trouble, annoyance, or extra effort. Step 3: Compare this with tranquillity, which refers to a peaceful, calm state and is almost the opposite of irritation. Step 4: Consider harmony, which means pleasant agreement or coordination, again not related to inconvenience. Step 5: Review rectitude, which means moral uprightness or correctness, having nothing to do with irritation or inconvenience. Step 6: Conclude that hassle is the correct one word substitute.

Verification / Alternative check:
Use the options in sample sentences. Saying The new registration process is an irritating inconvenience and The new registration process is a hassle both convey the same practical meaning. If you try to substitute tranquillity, harmony, or rectitude, the sentence becomes meaningless or contradictory: The new registration process is tranquillity does not make sense. This confirms that hassle fits the phrase and the others do not.

Why Other Options Are Wrong:
Tranquillity is wrong because it describes peacefulness, which is the absence of irritation. Harmony is wrong because it represents smooth cooperation or musical agreement, not inconvenience. Rectitude is wrong because it refers to moral correctness or righteousness, not to practical annoyance or difficulty. None of these conveys the idea of a small but annoying problem, which hassle does perfectly.

Common Pitfalls:
Students sometimes overlook informal but widely accepted words like hassle, believing that more formal sounding options must be correct. However, modern exam questions often include such common conversational terms. Always focus on meaning rather than formality. If you associate hassle with minor but annoying trouble and think of examples from daily life, you will easily remember it as a synonym for irritating inconvenience.

Final Answer:
The best one word substitute for Irritating inconvenience is Hassle.