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问题 选择题

利用PCR技术扩增DNA，需要的条件是

①解旋酶②引物③四种脱氧核苷酸④热稳定DNA聚合酶⑤目的基因⑥RNA聚合酶 [ ]

A．②③④⑤

B．①②③④

C．①③④⑤

D．①②③⑥

答案

答案：A

多项选择题

配电网按配电线路的不同，可分为（）配电网以及架空电缆混合配电网。

A.空中

B.架空线路

C.电缆线路

D.地埋
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单项选择题

Homely Hotels has a customer loyalty program in which for every four nights a customer spends at a Homely Hotel, he or she receives a coupon good for one free night at any Homely Hotel. Recently people have begun selling these coupons on the Internet for less than the cost of a night at a Homely Hotel. This marketing of coupons has resulted in decreased revenue for the Homely Hotel chain.
To discourage this undesirable trade in free-stay coupons, it would be best for Homely Hotels to restrict:（）

A. The number of coupons a customer can receive in one year.

B. Use of the coupons to the specific hotel in which they were issued.

C. The valid dates of the coupons to only the month immediately following the date of issue.

D. Use of the coupons to the recipient or people with the same last name.

E. Use of the coupons to Homely Hotel franchises that charge an equal or lesser nightly rate than the franchise that issued the coupon.
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