A:are doing
B:will do
C:will have been done
D:will be doing
用带电体去靠近吊在细线上的通草球时,会被带电体吸引过来,但接触后立即就离开了,请解释这个现象?
命题p:∃α,β∈R,使cos(α+β)=cosα+cosβ;命题q:直线x+y+1=0与圆x2+y-12=2相切.则下列命题中真命题为( )