以冷却方式运输冷藏货物时，通常每昼夜通风（）。
A．5～10次
B．20次以上
C．2～4次
D．6～8次
参考答案：C
The conservation area is very important for preserving many animals and plants, which would ______ run the risk of becoming extinct.
A．otherwise
B．therefore
C．though
D．instead
