He ______ at once when I promised to help him.

The invention of steam engine greatly sped up the industrial revolution, which _____ a lot to the take-off of the world. 

 At last the two companies ____an agreement and began to trade with each other .

During the Olympic Games,journalists from all over the world came to __________ the events.

Many difficulties have         as a result of the change over to a new type of fuel.