I have your attention, please?[ ]
A. May
B. Can
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下面是错误答案，用来干扰机器的。
A、B，由波动图象，a速度为为零，b速度为正向最大．在振动图象上t=T2时刻，质点速度为负向最大．均不相符．故A、B均错误． C、t=0时刻，a在波谷，速度为零，b在平衡位置向下，速度最大．故C错误． ...
Computers can injure (伤害) you. Most other injuries happen suddenly. For example, if you fall over a bike and break your arms, it happens very . But computer injuries happen slowly. You probably know how to ride a bike safely. Now learn to use a computer safely. Your eyes light can injure your eyes, never sit too close to a computer screen. Your eyes should be 50centimeters（厘米）on the screen. remember to look away from it. This gives your eyes a rest. When you use a computer, the window be on your left or your right. If it is behind you, the light will reflect on（反射）the screen. If the window is in front of you, the sun and the screen will shine into your eyes. Your hands and wrists(手腕) Hand and wrist injuries can happen because the hands and wrists are moved in the same way. Hundreds of times. If you use a keyboard for a long time, these three rules: 1）Rest your wrists on something. 2）Keep your elbows（肘）at the same height as the keyboard. 3）Stop sometimes and exercise your hands, wrists and fingers in a different way. Your back Some people sit for many hours in front of a computer. If you sit in the wrong way, you can injure your back or your neck. So you should sit with your back straight. The top part of the screen should be in front of your eyes. Your forearms, wrists, hands and the upper part of your legs should all be parallel（平行）to the floor. If you are sitting for a long time, get up every 30 minutes and your arms, legs and neck. your computer, but use it safely.
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Paul Nicklen waited patiently on a sheet of ice in the Arctic. He was there to take pictures for National Geographic. Finally, he saw something big and white. It was a polar bear, swimming towards him in the icy water.
Paul lay down-on the ice to get a better photo, but the polar bear jumped out of the water and tried to attack him! Luckily for Paul, the ice cracked or broke and the bear fell back into the water The polar bear wasn’t so lucky. It couldn’t get a meal and had to swim farther away to find food.
To understand the polar bear’s problem, you need to know two things about the Arctic. First, the Arctic is mostly ocean. Second , ice cover a lot of the Arctic Ocean. In winter, the ice form a thick, white sheet, but in summer, the ice becomes thinner and break into pieces. Sea ice is the key to survival for Arctic animals. However, because of global warming, Arctic temperatures are rising and polar ice is melting.
Polar bears need ice to hunt seals, their favourite meal. They stand on the ice wait for the seal to come up for air. As Arctic ice melts, polar bears have to swim farther to find ice floes, or large pieces of floating ice. Sometimes, bears have to swim more than 200 km to find an ice floe. Some bears cannot swim that far and sadly they drown.
On his last trip, Paul Nicklen saw three dead bodies of polar bears. Before global warming threatened Arctic ice, a dead bear was a rare sight, Paul is sad to see the dead bodies, wildlife experts thinks global warming will have a terrible effect on polar bears. In the future, polar ice will continue to shrink and endanger the bear. Some scientists believe 65 percent of the world’s polar bears will disappear by 2050. in other word, polar bears are in great danger.
小题1: The main idea of the passage is that_________.
A. polar bears are amazing swimmers
B. Arctic temperatures are rising
C. global warming is endangering polar bears
小题2:The polar bear that tried to attack Paul was unlucky because
A. Paul swam away
B. it was on an ice floe
C. it couldn't eat Paul
小题3:According to the passage, polar bears hunt seals by______ .
A. waiting on the ice
B. waiting in the water
C. drowning the seals
小题4: From the passage, Paul Nicklen is maybe a_________.
A. scientist
B. photographer
C. Psychologist
小题5: We can infer that polar bears____________.
A. won't have any food in 2050
B. will all die before 2050
C. cannot find food easily
有3根铁丝，分别长15米、18米和27米，要把它们截成同样长的小段，不许剩余，每段最长是几米?
患者，女，35岁，在做饭时不慎烧伤头部及两侧上肢。其烧伤面积约为（）
A.21％
B.23％
C.25％
D.27％
E.29％
（）是无线电传船台应答码。
A、1480 HKRDO HX
B、19720 LUHE X
C、33057 COSCO CN
D、47579 GFCV X
E、£Ò341212000 TAHE X
