Question

Physics a very interesting subject to study. Is, are, were, aren't,

Answer 1

Hey there! :D

Physics is a very interesting subject to study. 

All the other choices aren't grammatically correct. 

It is present tense, and the sentence is saying that it is a very interesting subject. It is. You wouldn't give it a negative correlation like 'aren't'. 

I hope this helps!
~kaikers