You don't have to __________ every new word in the dictionary while reading.
A:look for
B:look up
C:look at
D:look after
给下列字组词
幻____ 征____ 凡____ 艺____
幼____ 证____ 几____ 芝____
值____ 稍____ 统____ 般____
置____ 梢____ 流____ 股____
设m,n为两条不同的直线,α,β,γ为三个不同的平面,则下列四个命题中为真命题的是( )