单选题 At a certain state university last term, there were p students each of whom paid either the full tuition of x dollars or half the full tuition. What percent of the tuition paid by the p students last term was tuition from students who paid the full tuition?
(1)Of the P students, 20 percent paid the full tuition.
(2)The p students paid a total of $91.2 million for tuition last term.
(A) 条件(1)充分,但条件(2)不充分.
(B) 条件(2)充分,但条件(1)不充分.
(C) 条件(1)和(2)单独都不充分,但条件(1)和条件(2)联合起来充分.
(D) 条件(1)充分,条件(2)也充分.
(E) 条件(1)和条件(2)单独都不充分,条件(1)和条件(2)联合起来也不充分.

【正确答案】 A
【答案解析】[解析] (1)充分,因为由(1)中付全额学费的学生有20%,可以推知付全额学费的学生所付的学费所占的百分比为: