Water vapor in the lower atmosphere can vary in amount from a mere trace in arid regions to about 4 % by volume in moist areas 大气低层的水汽量在干燥地区（量）甚微，而在潮湿地区按体积占4 %左右。
2.
Bonus that can vary in amount from one year to the next either according to a predefined formulae or according to managements discretion 金额每年可变的花红，金额根据预先订定的公式计算或由管理阶层的酌情权决定
