Look at the mess the boys made! You _______ have taught them how to behave themselves.

We all know the truth ______ there are air, water and sunlight, there are living things.

With the help of high technology, in the past few years, electronic business __________          to bank industry, travel industry.

Out of the crowded bus             , who was dressed in a black suit and waved to a woman.

 Unfortunately, the element Madam Curie devoted all her life              her death.

 It’s certainly been a long time _________ we met last time.

 When first __________ to the market, the computer software was not a success due to its complexity in operation.

The young man insisted that he _________ nothing wrong and __________ free.

 It is ___________ the customers’ needs that has made chain stores so popular in big cities in China.

It remains doubtful whether the project _____________ next month will bring profits to the company.