Why the other options are wrong:

• His short tenure in Army Medical Corps.: The army career is background, whereas Watson identifies narrating detective cases as what makes him known.
• His friendship with Sherlock Homes.: Friendship alone is broader than the stated reason: narrating the detective’s cases.
• His grit and determination to serve people.: Determination to serve people is not the reason Watson gives for being known.

Correct Answer: He was his room partner.

Why this is correct: Watson says he shared Holmes’s rooms in Baker Street. They were room partners.

Why the other options are wrong:

• They both were doctors.: Watson’s medical training does not establish that both men were doctors, and it does not state their living arrangement.
• They both worked in army.: Watson’s army service does not establish shared service with Holmes, and it does not answer the housing question.
• He assisted Holmes in solving his cases.: Accompanying Holmes on cases describes their work together rather than their living arrangement.

Correct Answer: Assistant surgeon in the British Army.

Why this is correct: After university, Watson obtained a position as an assistant surgeon in the British Army.

Why the other options are wrong:

• Running a medical practice in a London hotel.: The source identifies army employment rather than running a medical practice in a London hotel.
• Dentist in the army.: The army role was assistant surgeon rather than dentist.
• Working in a private hospital.: The first job was with the British Army rather than a private hospital.

Correct Answer: He was too weak to serve the army.

Why this is correct: After Watson recovered, he remained very weak and could no longer serve the army. That was the immediate reason the doctors sent him home.

Why the other options are wrong:

• He was injured.: The wound was an earlier event; the narrowed question asks for the immediate reason after recovery.
• He was sick.: Watson had recovered, but remained weak. Continuing sickness is not the immediate reason given in that statement.
• He started working with Holmes.: Working with Holmes happened later and was not why the doctors sent Watson home.

Correct Answer: He used to receive pension from army.

Why this is correct: The army provided Watson with a small pension for nine months.

Why the other options are wrong:

• His relatives helped him.: Watson says he had no relatives to support him.
• He got a support from his friends.: Watson says he had no close friends in London; the support described is an army pension.
• He got a new job.: The stated source of money is a pension, rather than a new job.

Correct Answer: A hospital worker from Doctor Watson's student days.

Why this is correct: Watson met a hospital worker from his student days. That person knew someone looking for a flatmate and connected Watson with Holmes.

Why the other options are wrong:

• One of his close relatives.: The introducer is a hospital worker from Watson’s student days rather than a close relative.
• His army men.: The source identifies a former hospital worker rather than an army colleague.
• His landlord.: The person who introduces them is a hospital acquaintance rather than a landlord.