Statistics question (Ho / Ha concept)

When conducting a hypothesis test, the statements for Ho and Ha always pertain to:
a) mu
b) type 2 errors
c) the level of significance
d) the test statistic
e) population parameters
f) type 1 errors
g) sample statistics
h) pi
I) The probability that ho is true
j) mu sub d

I thought the answer was a) mu, but that was incorrect. Thanks for the help!!

e) population parameters