对承受动荷载和冲击荷载的焊件，要保证其焊后的强度和塑性、韧性满足要求，应选用的焊条为()。

A.氧化钛型焊条

B.纤维类型焊条

C.低氢型焊条

D.石墨型焊条

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

A．keep up

B．pick up

C．make up

D．catch up