A:Fe3+ SO42﹣ H+ Cl﹣
B:Mg2+ Cl﹣ OH﹣ Na+
C:H+ Ba2+ NO3﹣ SO42﹣
D:H+ Na+ K+ NO3﹣
小花的铅笔盒可以只放8只铅笔,只放圆珠笔可以放6只,如果放了4只铅笔,还可以放____只圆珠笔。
-- Would you like to play football after school?
-- ________. I have a lot of homework to do.