【简答题】Foam is a very effective smothering agent and ______.A. it provides cooling as a secondary effectB. works well on extinguishing electrical firesC. can be used to combat combustible metal firesD. All ...
【单选题】Production of mechanical foam by a portable in-line foam proportioner().
A.
increases the size of foam bubbles formed
B.
increases the rate of foam production
C.
improves the extinguishing properties of foam
D.
gives the nozzleman more freedom of movement,since it can be placed anywhere in the hose line
【单选题】用总体中各单位某一数量标志值之和除以总体单位总数,得到()。
【单选题】Foam is a very effective smothering agent and ______.
A.
it provides cooling as a secondary effect
B.
works well on extinguishing electrical fires
C.
can be used to combat combustible metal fires
【单选题】离差是总体各单位的标志值与算术平均数之差。离差的代数和为0,无法进行计算,所以先将各个离差求平方,以消除正负号的影响,然后求平均叫做__________。
【单选题】Foam is a very effective smothering agent and ______.
A.
it provides cooling as a secondary effect
B.
works well on extinguishing electrical fires
C.
can be used to combat combustible metal fires
【单选题】Foam is a very effective smothering agent and ______.
A.
it provides cooling as a secondary effect
B.
works well on extinguishing electrical fires
C.
can be used to combat combustible metal fires
【单选题】以总体各单位数值之和除以总体单位总数的商,即是______