单选题 At what speed was a train traveling on a trip when it had completed half of the total distance of the trip?
(1)The trip was 460 miles long and took 4 hours to complete.
(2)The train traveled at an average rate of 115 miles per hour Oil the trip.

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、 (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】 E

【答案解析】[解析] 因为题目中以及题设条件中都未给出火车在整个旅程中是匀速行驶的，所以无法根据平均速度求出某一特定时刻火车的速度，所以(1)，(2)以及(1)+(2)都不充分。