After working abroad for several years．Gill wants to settle down to a ____job in Britain．

A．normal

B．constant

C．permanent

D．primary

强心苷增强心肌收缩性的作用机制与下列哪种离子变化有关

A．心肌细胞内K⁺增加

B．心肌细胞内Na⁺增加

C．心肌细胞内Ca²⁺增加

D．心肌细胞内Mg²⁺增加

E．心肌细胞内Cl^-增加