Pretty simple SA question here. We are looking for an answer choice that will bridge the gap between the support and conclusion. I'll break it down in very simple conditional format.
Premise: public accommodation --> remove all physical barriers
Conclusion: Private schools --> remove all physical barriers
Assumption: Private schools --> public accommodation.
A. admissions is irrelevant here.
B. whether they have been is irrelevant as well. This answer choice says nothing about public accommodation.
C. bingo. This gives us the assumption we found in the argument. private schools --> public accommodation. Makes the argument airtight.
D. again, whether or not they do is irrelevant. This does nothing to bridge our gap.
E. public space is not the same as public accommodation.