甲状旁腺细胞分泌
A．胰岛素B．降钙素C．甲状腺素D．甲状旁腺素
参考答案：D
I know Beijing very well since I ________ there three times.
A. have been B. went C. have gone
在选用发动机冷却液时，其冰点要比车辆运行地区的最低气温低（）℃以上。
A．5
B．10
C．15
