At a price of $20 each, the demand for t-shirts from a group’s fundraising activity is unit elastic. Thus, the group’s total revenue from selling t-shirts __ at a price of $20 each.

At a price of $20 each, the demand for t-shirts from a group’s fundraising activity is unit elastic. Thus, the group’s total revenue from selling t-shirts __ at a price of $20 each.
A.will equal $1
B.will equal $0
C.reaches its minimum
D.reaches its maximum
正确答案：reaches its maximum