Final answer:
To rewrite the sentence in the interrogative form, start with the auxiliary verb 'were' followed by the subject 'they' and end with a question mark.
Step-by-step explanation:
The sentence given is 'They were absent yesterday'. To rewrite this in the interrogative form, we need to start with the auxiliary verb 'were' followed by the subject 'they'. So the correct interrogative form would be 'Were they absent yesterday?'
Learn more about Interrogative form in English