问题 选择题

用纳米氧化锆(ZrO2)氧化铝复合材料制成的人工髋骨和膝盖植入物,有良好的韧性,可使用30年之久.其中,能增强材料韧性的ZrO2中Zr的化合价为(  )

A.+1

B.+2

C.+3

D.+4

答案

因氧化锆为氧化物,则氧元素的化合价为-2价,

设氧化锆中锆的化合价为x,

由氧化锆的化学式为ZrO2,根据化合物中元素的化合价的代数和为0,则

x+(-2)×2=0

解得x=+4

故选D.

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What is Home stay? Literally it is a home for you to stay at when you are not at home. To be specific, home stay provides foreign language students with the opportunity to speak native language outside the classroom and the experience of being part of a British home. Here is what you will experience in our British Home-stay Program.

What to Expect

The host will provide accommodation and meals. Rooms will be cleaned and bedcovers changed at least once a week. You will be given the house key and the host is there to offer help and advice as well as to take an interest in your physical and mental health.

Accommodation Zones

Homestays are located in London mainly in Zones 2, 3 and of the transport system. Most hosts do not live in the town centre (Zone 1) as much of central London is commercial and not residential(居住的). Zones 3 and 4 often offer smaller accommodation in a more crowded area. It is very convenient to travel in London by underground.

Meal Plans Available

• Continental Breakfast

• Breakfast and Dinner

• Breakfast, Packed Lunch and Dinner

It’s important to note that few English families still provide a traditional cooked breakfast. Your accommodation includes Continental Breakfast which normally consists of fruit juice, cereal(谷物类食品), bread and tea or coffee. Cheese, fruit and cold meat are not normally part of a Continental Breakfast in England. Dinners usually consist of meat or fish with vegetables followed by desert, fruit and coffee.

Friends

If you wish to invite a friend over to visit, you must first ask your host’s permission. You have no right to entertain friends in a family home as some families feel it is an invasion of their privacy.

Self-Catering Accommodation in Private Homes

Accommodation on a room-only basis includes shared kitchen and bathroom facilities and often a main living room. This kind of accommodation offers an independent lifestyle and is more suitable for the long-stay student. However, it does not provide the same family atmosphere as an ordinary homestay and may not benefit those who need to practise English at home quite as much.

小题1:The passage is probably written for _____.

A.host willing to receive foreign students

B.foreigners hoping to build British culture

C.travellers planning to visit families in London

D.English learners applying to like in English homes小题2: Which of the following will the host provide?

A.Medical care.

B.Room cleaning.

C.Free transport.

D.Physical training.小题3: What can be inferred from Paragraph 3?

A.Zone 3 is more crowded than Zone 2.

B.The business centre of London is in Zone 2.

C.Hosts dislike travelling to the city centre.

D.Zone 1 offers bigger accommodation.小题4: According to the passage, what does Continental Breakfast include?

A.Dessert and coffee.

B.Fruit and vegetables.

C.Bread and fruit juice.

D.Centre and cold meat.