To solve this question, the user needs to know the correct grammar structure to use when talking about past habits.

The correct answer is "B. would play".

Explanation:

When talking about past habits, we usually use "used to" or "would" + the base form of the verb. In this case, the correct option is "B. would play" because it follows this structure correctly.

Option A, "use to play", is incorrect because it contains a spelling error - it should be "used to play" instead. However, this option is still incorrect because it is missing the auxiliary verb "would" or "used to" that is necessary to talk about past habits.

Option C, "were playing", is incorrect because it describes an action that was ongoing in the past, rather than a past habit.

Option D, "Were used to play", is incorrect because the verb "used to" should come before the main verb in the sentence. Additionally, this option is missing the auxiliary verb "would" that is necessary to talk about past habits.

Therefore, the correct answer is:

The Answer is: B. would play.