It is very kind ______ you to help me with my lessons because it is very difficult ______me to learn them well.

A．of; for

B．of; of

C．for; of

D．for; for

我国城市人群肿瘤死因中占第一位的是

A．胃癌
B．肝癌
C．支气管肺癌
D．食管癌
E．白血病