Mr.Hunter managed to         his neglect of his duty on the basis of his poor health. [ ]

A.remember                

B.forget

C.reject

D.justify

儿茶酚胺对心肌细胞的作用主要是（）

A.增加K⁺通道的通透性

B.增加Na⁺通道的通透性

C.增加Ca²⁺和K⁺的通透性

D.降低K⁺通道的通透性

E.增加Ca²⁺通道的通透性