低渗性缺水重度缺钠时，血清Na⁺（）。

A.低于140mmol/L

B.低于135mmol/L

C.低于130mmol/L

D.低于125mmol/L

E.低于120mmol/L

Lucy and I are in different _____, but we are good friends.

A．class

B．grades

C．grade

D．school