Measure their height or heights?

Hi. Please tell me which is correct. For this, let's say that there are a number of objects on the table and some students have to measure the objects' height, weight and size. As for the the teacher, he or she has to answer the following question. Thank you for your help in advance.

Q: What do they have to do?
A: They have to measure their (the objects') height (heights?), weight (weights?) and size (sizes).