Dear Wentao

 Please consult

https://sites.math.rutgers.edu/~zeilberg/Hist21/q5S.pdf

for the full solutions.

#1: wrong: 0 pts
#2: right 1 pt
#3: right 2 pts
#4(i): right: 4 points
#4(ii):  wrong: 0 points

So You got 7 points (out of 10).

 Best wishes,

   Dr. Z.