单选题 Experiments suggest that season of birth dramatically affects the speed ______ the body clock ticks.
A. at which B. for which C. on which D. in which

【正确答案】 A

【答案解析】[解析] 介词+which引导定语从句时，介词要与前面的名词搭配。本题中定语从句的先行词为speed，at speed意为“高速地”。句意：实验表明，出生的季节极大地影响了人体生物钟运转的速度。故选A。