调质的实质是回火。
参考答案:对
He is rather difficult to make friends with, but his friendship, _____ is more true than anyone else’s.
A.Once gaining
B.Once gained
C.Once is gaining
D.Once he gained
根据考古,()是已知的商代时期医学文字记录的载体。
A.竹简
B.石头
C.甲骨
D.帛
E.纸张