It ______twenty years since I came to the school. [ ]
A. are
B. is
C. was
D. were
答案:B
要从含盐16%的40kg盐水中蒸去水分,制出含盐20%的盐水,应当蒸去 (24) 水分。
A.6kg B.8kgC.10kg D.12kg