Teachers spend a large part of ___ working day preparing lessons.

• A. their
• B. his
• C. our
• D. my

Answer: (A)

Placing a possessive determiner that matches the subject is the key idea. Teachers is plural, so you need a plural possessive form. Their fits perfectly to show possession by the teachers in general. Using his would only refer to one male person, which doesn’t match the plural subject. Our would imply the speaker is part of the group, and my would refer to the speaker alone. With their, the sentence reads naturally: Teachers spend a large part of their working day preparing lessons.