MadeEasy Subject Test: Digital Logic - Circuit Output

Question

Some please tell how to solve this question ?

Answer 1

Option B is the answer, 

Caption

 

Answer 2

make transition diagram...

wave 1.draw i/p A first 

wave 2.then draw compliment of A with 10ns delay

wave 3.Take wave 1 & 2 draw AND of Both inputs 20ns delay

wave 4. draw wave 1 XOR wave 3  with 10ns delay!!... (result)