Does the object of the plural subjects in the following sentences also need to be plural?
1a. The kids need to complete their personal collage for homework.
1b. The student drivers couldn't figure out how to start their car.
2a. The kids need to complete their personal collages for homework.
2b. The student drivers couldn't figure out how to start their cars.
All of the above sentences are ambiguous. The subjects from the first pair could all be sharing the same object, the personal collage or car, and the subjects from the second pair could each have more than one of the object. Im wondering how I could construct a sentence where it's clear that each subject has just one of the object and is not open to misinterpretation.