Fill in the blank with the most appropriate word. They _________ basketball when I saw them. A. were playing B. played C. play D. are playing

The correct answer is: were playing.

The sentence is in the past tense, so we need to use a verb that is also in the past tense. The other options are not in the past tense, so they are not correct.

• Played is the simple past tense of the verb “to play”. It is used to talk about actions that happened in the past.
• Play is the infinitive form of the verb “to play”. It is used to talk about actions in general, or to talk about actions that are happening now or will happen in the future.
• Are playing is the present continuous tense of the verb “to play”. It is used to talk about actions that are happening now.

In this case, we are talking about an action that happened in the past, so we need to use the simple past tense. Therefore, the correct answer is “were playing”.