Question

who _____ (engage) in their morning exercise.

• A. was engaged
• B. were engaged
• C. had been engaged
• D. have been engaged

Answer 1

The correct option is B were engaged

Here, 'were engaged' in simple past tense is correct because it indicates an action that has already been completed. Here, the Army personnel 'were engaged'. The previous sentence is also in past tense.
'Was engaged' is incorrect because Army personnel is plural (were), not singular (was).
'Had been engaged' in past perfect continuous is incorrect because it is used to indicate an action in the past that began before a certain point in the past and continued up untill that time.
'Have been engaged' in present perfect continuous tense is incorrect because it is used to indicate an action that started at some point in the past and may or may not be complete.