离心泵扬程越高，升举介质的高度越高，泵产生的压力就（） A.越大 B.越小 C.不变

Before Alaska became part of the U.S., it had been owned by Russia. Trading posts and small settlements were scattered along the coast. The rest of land was left unexplored. The Russians were mainly interested in the wealth of furs from the vast herds of seals they found there.

By the mid-1800’s, most of the seal herds had been wiped out, and Russia no longer wanted to keep Alaska. William Seward, Secretary of State for President Johnson, believed the United States should buy Alaska from Russia. President Johnson wasn’t so sure it was a wise way to spend U.S. money, but he agreed to let Seward discuss it with the Russians. Acting quickly, Seward made a deal. On March 30, 1867, he signed an agreement for the U.S. to pay seven million dollars for the land.

Many people thought it was a foolish waste of America’s money. They called the deal “Seward’s folly”. Then gold was discovered in Alaska and public opinion changed quickly.

Seward did not live to see the true value of Alaska. He died in 1872, five years after making the purchase (购买). Each year, Alaska’s natural resources(资源) have brought in many times the $7,000,000 paid for it. Natural gas, coal, oil, lumber, seafood and other minerals, besides the gold first found, have made it a valuable addition to the United States. In 1959, Alaska be-came the 49th state of the United States.

小题1:The Russians wanted to sell Alaska because ______.

A．they thought it wasn’t a good place

B．they thought it didn’t belong to Russia

C．they couldn’t find enough seals there

D．they wanted to earn more money from the U.S.小题2:When Seward signed the agreement, many people thought ______.

A．it was a successful deal

B．it had its true value

C．he wasted U.S. money

D．he was clever小题3:Which of the following things was found first in Alaska?

A．Gas.

B．Coal.

C．Oil.

D．Gold.小题4:The best title for this passage would probably be ______.

A．Alaska, a beautiful place

B．Alaska with natural resources

C．Alaska, the 49th state of the U.S.

D．Alaska, home to seals

机泵在轴承润滑方面应注意那些问题？

知母清热泻火、生津润燥的药理学依据是什么？

下列有关公司债券与股票的区别有（）

A.债券是固定收益证券，股票多为变动收益证券

B.债券风险较小，股票风险较大

C.债券到期必须还本付息，股票一般不退还股本

D.债券在剩余财产分配中优于股票

反应炉冷启动的初始条件是什么？