-- Alice, how do your parents like pop music?
-- _____ my dad ______ my mom likes it. But they both prefer Beijing Opera.
A:Eigher; or
B:Neither; nor
C:Not only; but also
D:Both; and
想一想,填一填。
设向量a→=(1,-2),b→=(3,4),则向量a→在向量b→方向上的投影为____ .
下列运算,结果正确的是( )