— _______ do you improve your listening skills?
— I improve it _____ listening to English songs.
A：How; by
B：How; in
C：What; by
D：What; with
经过点P（﹣3，﹣4），且在x轴、y轴上的截距相等的直线l的方程是____ ．
①FeCl3 ②Fe2(SO4)3 ③Ca(HCO3)2 ④Na2CO3
