已知函数f(x)=sin(2x+π2),给出下面四个命题:①函数f(x)的最小正

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问题:

已知函数f(x)=sin(2x+
π
2
),给出下面四个命题:
①函数f(x)的最小正周期为π;
②函数f(x)是偶函数;
③函数f(x)的图象关于直线x=
π
4
对称;
④函数f(x)在区间[0,
π
2
]上是增函数,
其中错误命题的序号是______.
考点:真命题、假命题
题型:填空题

下列曲线表示四个不同的自然生态系统在受到同等程度的外来干扰后,初级消费者数量的变化情况。其中抵抗力稳定性最高的生态系统是[ ]

A.

B.

C.

D.

题型:填空题

蜗轮螺杆传动属于()机构。

A、平面齿轮

B、人字齿轮

C、斜齿轮

D、空间齿轮

题型:填空题

缓存(Cache)存在于______。

A.内存内部

B.内存和硬盘之间

C.硬盘内部

D.CPU内部

题型:填空题


Directions: There are 4 passages in this part. Each of the passages is followed by 5 questions or unfinished statements. For each of them there are 4 choices marked A, B, C and D. Choose the best one.
Passage One

American consumers like convenience very much. During the last 50 years, there has been a dramatic increase in such labor-saving devices as automatic washing machines, clothes dryers, dishwashers, food processors, microwave ovens, garbage disposals and power lawn mowers. Today, all of these and many more, are found in a typical suburban home. These labor-saving devices are designed to reduce the time spent on housework. However, the time that Americans save is quickly spent on other activities.
The American desire for convenience also created the concept of fast-food restaurants, found in every city and almost every small town in the United States, and now exported all over the world. These fast-food restaurants, such as McDonald’s and KFC, serve sandwiches, salads, fried chicken, seafood, and other food to hurried customers in five minutes or less, often at a drive-up window. There are also a wide variety of restaurants that will deliver Chinese food, pizza, and other dishes to people’s homes in about a half-hour. In many areas there are "take-out taxis" that will deliver food from the menus of 20 or 30 different restaurants for a small charge. For those who prefer to prepare their food at home, American grocery stores are full of convenience foods that are packaged and ready to cook or even precooked.
Like microwave ovens and dishwashers, fast-food and take-out restaurants are convenient because they save the American consumer time that would otherwise be spent fixing meals or cleaning up. More than half of all the women in the United States are currently employed. This includes mothers with children under the age of 18. More than half the women with little children under the age of six hold jobs. Sixty-eight percent of the women who have school-age children are employed. Families with working mothers need all the time-savers they can get.
Thus, the conveniences that Americans desire reflect not so much a leisurely lifestyle as a busy lifestyle in which even minutes of time are too valuable to be wasted. Alexis de Tocqueville was one of the first to see in this a curious paradox (自相矛盾) in the American character. He observed that Americans were so busy working to acquire comforts and conveniences that they were unable to relax and to enjoy leisure time when they had it. Today, many Americans have what one medical doctor has called "the hurry sickness".

It is implied in the passage that ______.

A.fast food is not as nutritious as home-cooked food

B.fast food restaurants are more popular than take-out restaurants in the U. S.

C.most of the cooking at home is done by women

D.more men than women prefer eating convenient food

题型:填空题

某住宅楼设计采用地面辐射供暖系统,下列设计选项哪一个是错误的

A.集、分水器之间设置旁通管
B.设置分户热计量装置
C.过滤器设置在分水器前
D.过滤器设置在集水器前

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