They tried to ____ hard plastics for metals in manufacturing machine parts. [ ]A. replace B. substit

These teachers try to be objective when they ___ t

He was unable to make much progress, hard ____ he tried.

If you try to sell people something that they______for free, they aren t going to buy it.A

Hard______they tried, they failed to climb to the mountain topA．ifB．when.C．asD．since

Most American newspapers try hard to entertain their readers because ______.A．they have to

Encourage your children to try new things, but try not to ___ them too hard.A. draw B.