钙、镁离子测定的参考方法是（） A.火焰光度法 B.邻甲酚酞络合铜法 C.过锰酸钾滴

在探讨某疾病的危险因素的研究中，在150名患该疾病的研究对象中，90名有A因子的暴露史，在200名未患该病的研究对象中，也有45名有A因子的暴露史，检验差异有统计意义。

该研究可得到的结论为（）。

A.A因子是危险因素

B.A因子是保护因素

C.A因子是混杂因素

D.A因子是无关因素

E.无法判断

下列各式中：

（1）-（-a³）⁴=a¹²；（2）（-aⁿ）²=（-a²）ⁿ；（3）（-a-b）³=（a-b）³；（4）（a-b）⁴=（-a+b）⁴正确的个数是（　　）

A．1个

B．2个

C．3个

D．4个

使物体带电的方法有三种，它们是（     ）

A．摩擦起电，感应起电，接触起电

B．物体放电，物体生电，摩擦起电

C．摩擦起电，感应起电，创造电荷

D．摩擦起电，创造电荷，接触起电

I knew nothing of the motives behind his recent move, and I don't know either the person to put him up to the action.

A．nor did I know ... who

B．not did I know ... that

C．nor do I know ... that

D．either did I know ... who

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence, you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

The ManStop, Boston’s hot new men’s clothing store, offers a selection that is on range from conservative pin-striped suits for that day at the office to stylish cashmere pullovers for that night on the town.（）

A. is on range from

B. ranging from

C. ranges to

D. ranges from

E. having ranged from