It _____ me 15 minutes to get to school on my bike. [ ]
A. costs
B. spends
C. takes
答案:C
A.
(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)单独不充分,但条件(1)和条件(2)联合起来也不充分.
已知m,n是正整数,则m是偶数. (1)3m+2n是偶数; (2)3m2+2n2是偶数.