The governor’s team of advisors, including her education and political strategists, has not been available for comment since the release of her controversial education reform proposal.
A) has not been available for comment since the release of her controversial education reform proposal
--> "has" is used properly as the subject is a collective noun "
team of advisors"
"her controversial education reform proposal" : we can look for a better word than "her", but the phrase "controversial education reform proposal" is best among all the other options.
B)
have not been available for comment since the governor released her controversial education reform proposal
--> we cannot use "have" as the subject is a collective noun"
team of advisors"
C) has not been available to make comments since releasing
her proposal on controversial education reform--> "her proposal on controversial education reform" : "her" is still here as in option A and "controversial education reform" now suggests not the proposal but the reform was controversial, which is not the intended meaning
D)
have not been available for comment since releasing her controversial education reform proposal
--> we cannot use "have" as the subject is a collective noun"
team of advisors"
E) has not been available to make comments since the release of
her proposal on controversial reform in education--> "her proposal on controversial reform in education" : "her" is still here as in option A and C ,and "controversial reform in education" suggests the reform controversial not the proposal same as option C
So, we have to stay with option A.
Hope this helps.