根据超固结比OCR可将沉积土层分类，当OCR<1时，土层属于：（）
A.超固结土
B.欠固结土
C.正常固结土
D.老固结土
参考答案：B
— By the way, _____ is your father?
— He's quite well, thank you. [ ]
A. who
B. what
C. how old
D. how
△ABC≌△DEF，∠A=30°，∠B=50°，求∠DFE=______．
