Q.A hollow flask retains its shape on heating because(1) it expands as if it were a solid body(2) only the outer surface expands(3) only the air inside it expand(4) only the inner surface expands.

Dear suhel

oprion 1 ic correct

it expand as if it were a solid body

Please feel free to post as many doubts on our discussion forum as you can.
If you find any question Difficult to understand - post it here and we will get you
the answer and detailed  solution very  quickly.

 We are all IITians and here to help you in your IIT JEE preparation.

All the best.
 
Regards,
Askiitians Experts
Badiuddin