2、Out of water, out of food, many people in New Orleans, US were in big trouble, crouching(蜷缩) on roofs of houses, waiting for ___55___. Floodwater were beating the walls a few metres below.

In early September, New Orleans was badly hit by Hurricane Katrina. The whole city was left in ___56___. Thousands of citizens lost their lives. Deaths figures are the biggest in the US since the San Francisco earthquake in 1993.

People feel very sad about the natural disaster. But we should also consider about the role human beings have played in ___57___ our natural environment.

Scientists point out that the flooding from Hurricane Katrina may have been caused by ___58___ activity. They believe the greenhouse effect has caused icebergs at both poles of the earth to ___59___, resulting in sea level rise. As most of the land in New Orleans lies below sea level, it is possible that sea level ___60___ could have had an effect.

Along the seafront, forests have been cut down to make ___61___ for hotels and restaurants. By losing this shield(盾牌)，the city seemed too weak to fight against Hurricane Katrina.

We have all learnt that nature is like a ___62___ net, where humans are just a very small part, together with animals, plants air and more. When we destroy some parts, the balance is broken and disasters arrive. Perhaps this is why more natural disasters are happening.

America produces the most greenhouse gas of all the countries. But it ___63___ to sign the “ Kyoto Protocol”(京都议定书)，which aims to limit its waste gas. Perhaps Hurricane Katrina will act as a(n) ___64___ to the US Government. It should also remind us that we should try our best to protect the earth before we regret it.