出现临床症状时,血小板的数量一般低于( )
A.200×109/LB.70×109/LC.120×109/LD.150×109/LE.170×109/L
参考答案:B
He came to my class every week, but his attitude ________ he was not really interested in the subject.
A.expressed
B.described
C.explained
D.suggested
具有支链的化合物A的分子式为C4H6O2,A可以使Br2的四氯化碳溶液褪色。1molA和1molNaHCO3能完全反应,则A的结构简式是______。 写出与A具有相同官能团的A的所有同分异构体的结构简式______