There is _____ a big apple on _____ desk.[ ]
A. an; the
B. a; an
C. an; a
D. a, the
答案:D
复乳WI/O/W2型,当W1不等于W2时是指下述哪一项()
A.一组分一级乳
B.二组分一级乳
C.二组分二级乳
D.三组分一级乳
E.三组分二级乳
奎宁碱