山药来源于

A．主产于河南
B．主产于山西、河南、河北
C．主产于甘肃
D．主产于四川、湖北
E．主产于江苏、湖北、河南

It was spring _____ my mother bought me a mountain bike and I started learning cycling. [ ]

A. that

B. when

C. in which

D. where