车外圆时，如果主轴转速增大，则进给量（）A、增大 B、减小 C、不变 D、不确
题型：单项选择题
问题：
车外圆时，如果主轴转速增大，则进给量（）
A、增大
B、减小
C、不变
D、不确定
题型：单项选择题
You are probably familiar with the saying：An apple a day keeps the doctor away. A recent research carried out by the Chinese University of Hong Kong may change the saying:
An apple a day may keep aging away.
The research chose fruit flies(果蝇), as they share many genes(基因)with humans. The fruit flies were either fed normally or had an apple extract(浓缩物) added to their diet.
It turned out that those fruit flies that were given apple extract lived about 55 days—five days longer than the flies that were normally fed. The research group also found it easier for the flies to walk，climb and move about as they aged.
According to the result, the researchers believed that the antioxidants(抗氧化剂) in the apple extract helped clean up dangerous chemicals(化学物质) that cause illnesses，as well as aging.
In another study，researchers examined diets of thousands of women. They discovered that those who regularly ate apples were 20 percent less likely to suffer heart illnesses and stroke.
The apples’ genetic code(遗传密码) was discovered recently. It allows scientists to develop nicer and healthier fruits. Researchers are already using the information to grow a kind of apples full of antioxidants that can keep eyes and joints healthy and protect humans against heart illnesses and cancer.
Apples that kill the desire(欲望) to eat could also be produced, with the first“extra-healthy’’apples on supermarket shelves within just four or five years.
T
he team that keeps studying apple DNA includes 100 scientists from five countries. Their research also suggests that around 65 million years ago, when dinosaurs began to die off the plant，which would finally become today’s apple tree, experienced a great genetic change. The number of many of its genes doubled. The extra genes allowed the apple to get used to worse conditions and go through a different development from peaches，strawberries and other related fruits.
小题1:Why were fruit flies used for the research?
A．Because they have a similar diet to humans.
B．Because they have a history as long as apples.
C．Because they share a lot of genes with humans.
D．Because they feed on nothing but apple extract.小题2:What result did the researchers find out?
A．Apples produce chemicals that can change hu
man genes.
B．Apples have antioxidants that kill chemicals that cause aging.
C．Apples are rich in vitamins that are needed in humans’bodies.
D．Apples produce chemicals that make apples taste more delicious.小题3:What happened to apples around 65 million years ago according to the research?
A．Their genes stopped their development as the environment got worse.
B．Their genes became twice in number but they finally died off like dinosaurs.
C．They experienced a great genetic change making them used to worse conditions.
D．They went through a similar development to peaches, strawberries and other related fruits.小题4:What can we infer(推断)from the passage?
A．Eating apples may bring us more advantages than we might believe before.
B．People who have the habit of eating apples don’t need to see a doctor.
C．Apples that kill the desire to eat are already available in supermarkets now.
D．People will eat apples instead of peaches and strawberries from now on.