Explanation:

- The first part of the sentence, "your body doesn’t (2)______ the sleeping time," suggests the body is active while you sleep.

- In this context, the sentence is explaining what occurs while you are asleep.

- Let's evaluate the options for blank no. 3:

- Option 1: where – Implies a location, which doesn't fit the context.

- Option 2: why – Implies a reason, does not explain the body's activities during sleep.

- Option 3: when – Indicates timing, which is appropriate because it relates to the body's activities happening during sleep.

- Option 4: what – Implies a description of an activity, but doesn't fit as naturally as "when."

- The sentence is trying to say: "what happens during the time you are sleeping."