癌基因异常是肿瘤发生的主要原因，癌基因是（）。 A.肿瘤细胞独有的基因 B.由病毒带

The course normally attracts 20 students per year, ____ up to half will be from overseas.

A．in which

B．of whom

C．of which

D．for whom

Neil has three friends in the school. They are all________.

A．woman teacher

B．woman teachers

C．women teacher

D．women teachers

能说明苯分子中的碳碳键不是单双键交替的事实是：①苯不能使KMnO₄溶液褪色；②苯环中碳碳键的键长键能都相等；③邻二氯苯只有一种；④间二甲苯只有一种；⑤在一定条件下苯与H₂发生加成反应生成环已烷。

A．①②③④

B．①②③

C．②③④⑤

D．①②③⑤

何谓Cushing溃疡?

线虫不危害植物。