Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?

(1) She bought $4.40 worth of stamps.

(2) She bought an equal number of $0.15 stamps and $0.29 stamps.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案怎么能是D呢？

我认为应该选A：

（1）条件1就是求所有满足15m + 29n = 440 的非负整数{m,n}，简单的计算可知惟有{10，10}能满足此式，因此，条件1是充分的。

（2）条件2应该是不充分的，因为不知道Joanna 所买的邮票的总价值，（15 + 29）m = 44m=??，非负整数m无法确定。