Why is the answer to this Python Challenge Error?

Question

A = [1 , 2]
B = [3 , 4]
C = A.extend(B)
print(C[3])

Answer 1

You added [3,4] to A so A is extended. Therefore Print A[ ]

A = [1 , 2]
B = [3 , 4]
C = A.extend(B)
print(A[3])

#And try A[0], A[1], A[2]

Answer 2

Try to run below for extend help. You will get the answer.

print(help([].extend))