一位中学生的质量大约是 （ ）
A．50g
B．50kg
C．5kg
D．500kg
答案：B
一位中学生的质量大约是50kg。
They had to walk ______the jungle because their car broke down. [ ]
A. across
B. through
C. on
D. under
下列叙述哪项是错误的
A．血液中水占78-82g/100ml
B．由于水比热大，有利于维持体温
C．血浆含水量与红细胞含水量相等
D．水参与维持渗透压和酸碱平衡
