正确答案: AC

心室容积不发生改变 房室瓣和半月瓣都关闭

题目：等容收缩期的特点是（　　）

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学习资料的答案和解析：

[单选题]-- How do you like these chairs?-- Yes, they are actually nice but they are not much ________ demand now．

on

解析：On demand固定词组，意为：需求。选项B是正确的。【句子大意】你觉得这些椅子怎么样?不错，它们的确很好。可我们现在不需要。

[单选题]More has been learned since 1945 about the chemical changes in the body than in all human history before ________ time．

that

解析：这里指的是在1945年之前的那个时期，并有强调之意。选项B是正确的。【句子大意】自从1945年以来，我们对人体化学变化的了解比1945年之前的整个人类历史所了解的还要多。

[单选题]_________

根据以下内容，回答下面的题目。Insure means to protect _51_ a loss of money．Most people can budget their money so that their income will cover expected expenses _52_ food, clothing, housing, and public services．But, there is no way to know _53_ who will suffer a crisis (危机) such as a serious illness, fire, flood, or a car accident．Such crises usually _54_ great expense．Even if people could predict crises, it would be hard to save enough money to _55_ the expenses．Insurance is a system _56_ a company collects money from many individuals and then pays certain expenses whenever one of those insured individuals is faced with a certain crisis．An insurance policy _57_ how much the insurance costs and how much the company will pay when a policy holder is faced with a certain crisis．There are many different kinds of insurance, _58_ hospital, motor-car and fire．Insurance can be rather expensive but most people buy insurance of some kinD．Insurance is something _59_ people buy and hope they will _60_ need．_________

by which

[单选题]You can borrow that bicycle if you________．

want to

[单选题]

[单选题]卵巢的形态（　　）

性成熟期卵巢最大

[单选题]胃酸分泌减少时，促胰液素的分泌（　　）

减少