问题 选择题

置换反应指的是(  )

A.一种单质和一种化合物作用生成另一种单质和另一种化合物的反应

B.有单质和化合物生成的反应

C.有金属和非金属生成的反应

D.有单质和化合物参加的反应

答案

A、单质与化合物反应生成单质和化合物,符合置换反应,故A正确.

B、有单质和化合物生成的反应,反应物不一定是单质和化合物,如氯酸钾分解生成氯化钾和氧气,故B错误..

C、有金属和非金属生成的反应可能是化合反应,如铁和氧气反应生成四氧化三铁,故C错误.

D、有单质和化合物参加的反应,生成物不一定有单质和化合物,如二氧化硫和氧气的反应生成三氧化硫,故D错误.

故选A.

单项选择题
单项选择题

The face of the 21sl century is already growing in a laboratory. Getting a piece of the new look could soon be as simple as writing a cheque.

Scientists in recent years have made giant leaps in the artificial production of skin, bones and tissue. While their research has been motivated by a desire to help accident and medical victims, their work is about to go commercial.

The burgeoning (萌芽) cosmetic surgery market has snapped up the technological advances. By the turn of the 21st century, changing your face or improving your body will be limited not by your imagination or desire, but by the size of your bank account.

And there is even work being done on that, with the costs of cosmetic surgery being cut to make it affordable and accessible for the average woman and her partner.

"It’s no longer a vanity thing, it’s simply making use of the available technology to improve those parts of the body you might not be happy with, " Cindy Clovetti, a Toronto-based skin and beauty care expert, said. "People who 10 years ago said they would never use a computer and would never get a boob job (胸部整形手术) are now surfing the web getting, the latest information for their next operation. "

Latest figures in the United States indicate the number of patients receiving cosmetic surgery in 12 months will top the magic million within two years (there were 850000 last year), while the number of men seeking image-improving operations has increased 35 percent in the past four years.

Breast implants are now very much a bread-and-butter job for many cosmetic surgeons and the big advances have been made in the development of bone implants which can produce instant high cheek bones, sculpture better shaped noses and ears and give men the chisel-shaped jaw that is always a sure-fire (必定成功的) chick-magnet (吸引女人的东西).

British futurologist Ian Pearson speculates that by 2020, up to 96 percent of body weight will be replaceable with the brain being the only organ not interchangeable. "By 2020 you could have a new face, or new skin, and by 2030 a fully working replacement body part. By the end of the 21st century, people will be able to get an entirely new body. \

According to Ian Pearson, ()。

A. brain will be replaceable by the end of the 21st century

B. the entire body can be replaced by 2030

C. people will be able to get a fully working replacement body part by 2020

D. people will be able to have a new face and skin by 2020