Scientists will have to come_______ new methods of increasing the world’s food supply.

The schoolmaster hesitated ___ an instnat before he made the decision.

It was generally believed that the show was not as successful as expected, but____, I think it was a great success.

It seems that living green is  ______easy and affordable. A small step masks a big difference. 

Progress so far has been very good.______，we are sure that the project will be completed on time.