My cousin and I took a trip by rail across Canada from west to east. Before starting out, we spent a couple of days in Vancouver, admiring the     1    (sight). Then we arose early to take the train to Lake Louise, passing through the Canadian Rockies.     2    (see) from the train window, the mountains and forests looked     3    (mass). We spent the night near the lake, where the blue water literally took our breath away,     4     headed to Jasper the next morning. The beautiful scenery convinced us it was the most awesome journey we     5    (take). From Jasper, we boarded the train bound     6     Toronto. One of our first stops was in Edmonton, which     7     (be) home to many shopping malls. We never anticipated seeing such an open country until the train headed across the Great Prairie.     8     amazed us most were a bunch of farms covering two wheat- growing provinces. The train thundered on, through the     9    (roll) hills in Ontario. It was     10    (true) enjoyable to watch the red maple leaves outside the window. After four days, we reached Toronto.

2 . Coral reefs are some of the most diverse and valuable ecosystems on Earth. Coral reefs support more species per unit area than any other marine (海洋的) environment, including about 4,000 species of fish, 800 species of hard corals and hundreds of other species. Scientists estimate that there may be millions of undiscovered species living in and around reefs. This biodiversity is considered the key to finding new medicines for the 21st century. Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, viruses, and other diseases.

Healthy coral reefs support fisheries as well as jobs and businesses through tourism and recreation. About half of all managed fisheries depend on coral reefs and related habitats for a part of their life cycles. The National Marine Fisheries Service estimates the commercial value of U. S. fisheries from coral reefs is over $ 100 million, Local economies receive billions of dollars from visitors to reefs through diving tours, recreational fishing trips, hotels, restaurants, and other businesses based near reef ecosystems.

Coral reef structures also buffer (缓冲) shorelines against 97 percent of the energy from waves, storms, and floods, helping to prevent loss of life, and property damage. When reefs are damaged or destroyed, the absence of this natural barrier can increase the damage to coastal communities from normal wave action and violent storms. Several million people live in U. S. coastal areas near coral reefs. Some coastal development is required to provide necessary infrastructure (基础设施) for coastal residents and the growing coastal tourism industry.

Despite their great economic and recreational value, coral reefs are severely threatened by pollution, disease, and habitat destruction. Once coral reefs are damaged, they are less able to support the many creatures that live on them and the communities near them. When a coral reef supports fewer fish, plants, and animals, it also loses value as a tourist destination.

The Xi’an City Wall is the most complete city wall that has survived China’s long history. It     1     (build) originally to protect the city     2     the Tang dynasty and has now been completely restored (修复). It is possible       3     (walk) or bike the entire 14 kilometers.

We accessed the wall through the South Gate. The wall is 12 meters high and from here you can see streams of people moving inside and outside the City Wall.

After     4     (spend) some time looking at all the defensive equipment at the wall, we decided it was time for some action and what     5     (good) than to ride on a piece of history!

We     6     (hire) our bikes from the rental place at the South Gate. My bike was old and shaky     7     did the job. It took us about 3 hours to go all     8     way around the Xi’an City Wall. Supposedly you can do it in two hours, but we stopped at the different gates and     9     (watchtower) to take pictures or just to watch the local people going about their     10     (day) routines.