100t含氧化铁质量分数为80%的赤铁矿石，理论上可炼出含铁96%的生铁的质量是（　　）

A．56 t

B．58.3 t

C．70 t

D．72.9t

Without proper lessons, you could ______ a lot of bad habits when playing the piano.

A．keep up

B．pick up

C．draw up

D．catch up