下列各项中,不是离心泵产生振动的原因为()。A、转子不平衡 B、泵轴和电机轴中心线不

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问题:

下列各项中,不是离心泵产生振动的原因为()。

A、转子不平衡

B、泵轴和电机轴中心线不对

C、气蚀和抽空

D、出口阀开度偏小

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Sydney—A shark savaged a schoolboy’s leg while he was surfing with his father at a beach in Sydney on February 23. It was the third shark attack along the coast of Australia’s largest city in a month.

The 15­year­old boy and his father were in the water off Avalon, on Sydney’s northern beaches, around dawn when he was attacked. The city’s beaches are packed with locals and tourists during the summer months.

“The father heard a scream and turned to see his son thrashing (激烈扭动) about in the water,” police said. “Fortunately, the shark swam away and the boy was helped to the shore by his father.”

Lifesaving Club spokesman Nick Miller said, “It got him around the top of his left leg and the father came and dragged him out of water.” He said the boy was bleeding heavily when he was brought to the shore. “There was a lot of pain, as you can imagine.” The teenager was airlifted to hospital for treatment for leg injuries.

Police said the bites “cut through to the bone”, but the boy did not appear to have sustained any fractures (骨折). He was in a stable condition now.

Several beaches were closed after the attack. Water police and lifeguards were searching for the shark, while police hoped to identify its species by the shape of the bite marks. But they said it was too early to say what type of shark attacked the boy. “I don’t even know if he saw it,” Miller said.

Many shark species live in the waters off Sydney’s beaches, but attacks on humans are still relatively rare. However, there were two attacks on successive days earlier this month, one on a navy diver in Sydney harbor,not far from the famous Opera House, and the other on a surfer at the city’s world­famous Bondi beach.

Fishermen say shark numbers are on the rise. There is a ban on commercial fishing in the harbor, which has increased fish stocks. Marine experts also claim environmental protection has created a cleaner environment, attracting sharks closer to the shore as they chase fish. Many shark species, including the Great White—the man­eaters made famous in Steven Spielberg’s Jaws—are protected in Australian waters.

小题1:The report mainly tells us________.

A.shark attacks on humans are on the rise

B.sharks attacked humans three times in one month

C.a boy was attacked by a shark at a Sydney beach

D.shark numbers are increasing in the waters off Sydney’s beaches小题2: The underlined word “savaged” in the first paragraph probably means “_____”.

A.attracted

B.dragged

C.bit

D.packed小题3: What do we know about the city of Sydney from the passage?

A.It is one of the largest cities in Australia.

B.Sydney harbor is not far from the famous Opera House.

C.There are many locals and tourists on its coast all the year round.

D.There are few shark species in the waters off Sydney’s beaches.小题4: About the injury of the boy we know that________.

A.he was losing much blood when he was dragged out

B.he was very nervous when he was sent to hospital

C.he may be in danger of losing his leg

D.he was injured in the right leg小题5: All the following are the causes of Australia’s sharks’ increasing except that___.

A.environmental protection has created a cleaner environment

B.a ban on commercial fishing has increased fish numbers

C.many shark species are protected in Australian waters

D.the film Jaws has made the Great White famous

题型:单项选择题

糖类摄入过多引发的高脂血症通常为()。

A.Ⅰ型

B.Ⅱ型

C.Ⅲ型

D.Ⅳ型

E.Ⅴ型

题型:单项选择题

在一个施工现场有甲、乙两个独立承包人同时施工,由于施工出现交叉干扰,致使甲、乙分别受到一定损失,总监理工程师向甲发出了暂停施工指令,则()。

A.甲、乙都应向发包人索赔

B.甲,乙分别承担对方的损失

C.甲、乙分别承担各自的损失

D.甲的损失由发包人承担,乙的损失自行承担

题型:单项选择题

一般认为,西方文化的三条根分别是()。

A.古希腊文化

B.希伯来文化

C.玛雅文化

D.罗马法

题型:单项选择题

仓泵上平衡管的作用是()

A.输送

B.密封

C.流化

D.排除空气

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