Only two test cases getting passed, rest showing exception

I am getting the following result on submitting my assignment.
Test 1 : PASSED Test 2 : PASSED Test 3 : EXCEPTION Test 4 : EXCEPTION Test 5 : EXCEPTION Test 6 : EXCEPTION Test 7 : EXCEPTION Test 8 : EXCEPTION
Kindly please guide me what is the meaning of the exception and how can I sort my mistakes

please help regarding the solution

Not sure if you mean assignment 1 really here.

If so, there are tests inside your notebook. Did your solution pass them successfully?