—What are you doing?
—I am _________ a letter.[ ]
A. write
B. writing
C. writes
答案:B
It has been many years since I was last in London, _______ I still remember something that happened during that visit.
A.and
B.for
C.but
D.as
水-醇法测定巴比妥类药物的含量时,以下叙述正确的是
A.本类药物溶解度较大,除水-醇法外,通常还在碱性溶液中进行酸碱滴定法
B.该法测定药物含量时,可以避免弱酸盐类药物易溶于水而产生的干扰
C.以溴酚兰作为指示剂
D.电位法指示终点不能采用
E.用麝香草酚酞为指示剂