用于空翻物件的起重机，应具有主、副两套起升机构。（）
A、正确
B、错误
参考答案：A
---- We’re organizing a party next Saturday, and I’d like you to come.
---- _______! I have another one that day. Thank you just the same.
A．Good luck
B．What a pity
C．Never do it again
D．Well done
气候对土壤有机质的影响
