If r and t are positive integers, is rt even?
(1) r + t is odd.
(2) rt is odd.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
(2)r为偶数时,t为奇数或者偶数均符合,所以不充分