【单选题】Most Jewish families ________ many difficulties during the Second World War.
【多选题】一般来说,幼儿美术活动目标设定要从以下几个角度考虑。( )
【单选题】During working, thermostatic expansion valve should be ().
A.
either all the way open or all the way closed
C.
throttled depending on load
D.
controlled by liquefied pressure
【单选题】下列关于肾上腺的描述错误的说法是
D.
右肾上腺在右肾上极稍上,左肾上腺在左肾上极靠内
【判断题】对称矩阵 A (简称对称阵),其转秩矩阵 与原矩阵 A是 相等的。
【单选题】关于矩阵的秩,下面说法正确的是( )
A.
任意一个非零矩阵在转化成阶梯形矩阵的过程中每一个矩阵的秩都是 r(A)
B.
矩阵 A 经过初等变换必须化为最简阶梯形矩阵 B 时, B 的非零行的行数称做矩阵的秩
【单选题】During the valve overlap period, the exhaust pressure of a turbocharged four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure ______.
A.
effective cylinder scavenging and cooling
B.
constant pressure from the turbochargers
C.
cooler operation of the exhaust system
D.
effective constant pressure for turbocharger operation