正铲挖掘机的挖土特点是（）。
A、前进向上，强制切土
B、前进向上，自重切土
C、后退向下，强制切土
D、后退向下，自重切土
参考答案：A
_____ she couldn't understand was _____ fewer and fewer students showed interest in her lessons. [ ]
A. What; why
B. That; what
C. What; because
D. Why; that
This magazine ______ out _____ the morning of March 1st.
A．came, in
B．came, on
C．was come, in
D．was come, on
