I would have helped you, but I       __ really occupied the whole week．

A．was

B．am

C．had been

D．were

下列烯烃和HBr发生加成反应只能得到一种产物的是（     ）

A  CH₂=CH₂             B  CH₂=C（CH₃）₂

C  CH₃CH=CH₂          D  CH₃CH₂CH=CH₂