When the A(concentration) of calcium in the blood is B(too) low, the parathyroid glands C(began) to D(secrete) the hormone parat

admin2011-03-14  13

问题 When the A(concentration) of calcium in the blood is B(too) low, the parathyroid glands C(began) to D(secrete) the hormone parathormone.

选项

答案C

解析 began to secrete改为begin。主从句的时态保持一致。
转载请注明原文地址:https://jikaoti.com/ti/LVXYFFFM
0

最新回复(0)