Complete the following sentences and explain why they are correct: He spoke in a low voice for fear he _ wake up the body. She raises her hand in order _ ask a question.

Here are the completed sentences:

3. He spoke in a low voice for fear he should wake up the body. This sentence is grammatically correct. The phrase "for fear he should wake up the body" indicates the reason for speaking in a low voice, which is to prevent the feared outcome of waking up the body.

4. She raises her hand in order to ask a question. This sentence is also grammatically correct. The phrase "in order to ask a question" clearly states the purpose for which she raises her hand.

Both sentences are correctly completed.