已知y与x成正比例，当x=-2时，y=6，那么比例系数k=______．
设y=kx，当x=-2时，y=6，
则6=-2k，
解得，k=-3．
故答案为-3．
–Can you guess if they ______ to play basketball with us?
–I think they’ll come if they _____ free.
A．will come; are
B．will come; will be
C．come; are
D．come; will be
所有被子植物的雄蕊由花丝和花药两部分组成。
