In the sentence "He is now looking about a job.", the underlined preposition must be checked. Choose the option that best improves the phrase, or select No improvement if the sentence is already correct.

Introduction / Context:
This sentence improvement item tests correct prepositional usage with the verb look. In English, different prepositions with look create different meanings, such as look for, look after, look into, and look about. The sentence describes someone trying to find employment, so you must choose the preposition that expresses the idea of searching or trying to find something.

Given Data / Assumptions:

• Sentence: He is now looking about a job.
• The underlined part is looking about a job.
• Options: for, after, into, No improvement.
• The intended meaning is that he is trying to find a job at present.

Concept / Approach:
The correct phrasal verb in English for searching is look for. We say look for a job, look for a house, or look for a solution. Look about can mean look around in a physical space, but not search specifically for something, so looking about a job is incorrect. Look after means take care of, and look into means investigate, both of which change the meaning of the sentence. Therefore, the correct preposition is for, giving the expression looking for a job.

Step-by-Step Solution:
Step 1: Identify the core verb: looking. The sense is clearly that he is trying to find employment. Step 2: Recall that the standard English expression is look for something when you are searching for it. Step 3: Replace about with for to obtain looking for a job. Step 4: Check option A, for, which yields: He is now looking for a job. This is natural and correct. Step 5: Examine option B, after. Look after means care for, as in look after children or look after the house, which does not match the context of job hunting. Step 6: Examine option C, into. Look into means investigate or examine, as in look into a matter, which is also not appropriate here. Step 7: Reject No improvement because looking about a job is not idiomatic in standard English.

Verification / Alternative check:
Check the sentence against common examples: She is looking for a new apartment, They are looking for a better opportunity, He is looking for a part time job. All of these use look for plus the thing being sought. There is no standard pattern look about a job in English to mean search for employment. This comparison confirms that for is the only suitable preposition to express the intended meaning.

Why Other Options Are Wrong:
Look after a job would mean take care of a job that you already have, which does not describe someone who is unemployed. Look into a job would suggest investigating a job opportunity, not being in general search of employment. No improvement keeps the incorrect combination look about a job.

Common Pitfalls:
Because many phrasal verbs are formed by look plus different prepositions, learners sometimes mix them up. The safest strategy is to learn each verb and preposition pair as a fixed unit: look for to search, look after to care for, look into to investigate, and so on. Being familiar with these fixed patterns will help you quickly recognise incorrect combinations such as look about a job and correct them in exam questions.

Final Answer:
The correct improvement is for, giving: He is now looking for a job.