[简答题]Maintaining an energetic presence is very difficult to do unless______.

[简答题]Meaningful studies on this topic are very difficult to perform because they require large populations of subjects and many years of data collection, and because poor health sometimes results in limitations to physical activity.

[填空题]Women and children are those who are very difficult to be infected HIV/AIDS.

[单项选择]Casa ltaliana
Twenty years ago, it was difficult to find fresh pasta in Britain without going to an Italian restaurant. For this reason, Marco and Mariengeladi Bietro, owners of a small but busy Italian restaurant in the Scottish city of Glasgow, found themselves approached by a local Italian food store wanting to stock their pasta. Other foodstores followed this example and soon Marco and Mariangela were supplying them on a large scale as well as running a restaurant. But despite the long hours they were working, Marco and Mariangela did not consider changing career or moving from Scotland. It was only years later that they realised which business made more sense.
So in 1981, Marco and Mariangela sold their restaurant, bought a former factory and moved to the English countryside. They both miss city life. Although suitable property in the country was cheaper than in the city, it was only the thought of trucks wasting hours driving from Scot
A. They were attracted by a job which offered shorter working hours.
B. They had been searching for a very profitable business.
C. They learned that demand for fresh pasta was hig

[填空题]Not having got enough hands, we had great difficulty in carrying out the task.

[单项选择]Able-bodied people just don’t realize how difficult it is _________ good jobs.
A. of disabled people to get
B. of disabled people getting
C. for disabled people to get
D. for disabled people getting

[单项选择]（）to some parts of South America is still difficult, because parts of the continent are still covered with thick forests.
A. Orientation
B. Access
C. Procession
D. Voyage

[单项选择]Regular exercise can keep you energetic and contribute to a productive life in the long run.（　）
A. athletically
B. successively
C. ultimately
D. persistently

[填空题]Maintaining an imperial tradition that originated from the Zhou Dynasty( c. 1066-221 BC) ,the Ming emperors selected the location and design of their tombs while they were still alive. The selection of sites, based on the prevailing winds and the water level, ensured that only benevolent spirits were inhabiting the area. Of the 16 Ming emperors, 13 chose to be buried in this serene valley (Shisanling) just north of Beijing.
　　The Sacred Way. The road to the tombs, which branches off the route to the Great Wall, was once a 6.4km. (4mi.)long sacred way, forbidden to all but the emperor’s funeral cottege. The road begins at a five-arched marble gate, built in 1540. A mile further down stands a three-arched gateway, the Dahongmen( Great Red Gate).
　　The emperor’s body was carried through the central archway. Only on this one occasion was the center door opened. Just beyond the gate sits a huge stone tortoise( symbol of longevity) with a 9.1m. (30ft.) stele mounted on its back.