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问题 单项选择题

磨菜刀时要不断浇水，是因为( )。

A．为了冲洗磨刀时产生的琐屑

B．浇水可以增加刀与磨刀石的摩擦，从而使刀磨得更利

C．为了降低摩擦时刀的温度，从而使磨过的刀口更利

D．磨刀石太干了不好用

答案

参考答案：C

解析： 磨菜刀时要不断浇水，是因为菜刀与石头摩擦做功产生热使刀的内能增加，温度升高，刀口硬度变小，刀口不利；浇水是利用热传递使菜刀内能减小，温度降低，不会升至过高。故选C。

阅读理解

Wonderful Museum
Hours
Monday – Thursday: 10:00 am – 5:00 pm
Friday: 10:00 am – 8:00 pm
Saturday: 10:00 am – 5:00 pm
Sunday: 11:00 am – 5:00 pm
Closed on Thanksgiving Day and Christmas Day.
The Museum Shop is open during regular museum hours.
The Museum Library   
Monday –Friday: 10:00 am – 5:00 pm
The Skyliner Restaurant
Monday - Saturday: during regular museum hours
Sunday: 11:30 am – 5:00 pm
Admission
Adults:$7.00
The aged and students with ID: $6.00
Wonderful Museum offers a 50% discount to groups of 20 or more.
小题1:Wonderful Museum usually opens ____ except on Thanksgiving Day and
Christmas Day.
A．from Monday to ThursdayB．every dayC．every day of the weekD．on weekdays
小题2:If a group of 30 students with ID visit Wonderful Museum, how much should they pay for the admission?
A．$ 105.B．$ 90.C．$ 210.D．$ 180.
小题3:You can borrow books from the Museum Library ____.
A．on weekdaysB．at weekends C．from Monday to SaturdayD．at 9:00 am
小题4:If you want to invite your friends to dinner on Friday, you have to reach the Skyliner Restaurant ____.
A．after 8:00 pmB．at 6:00 am C．after 10:00 pmD．before 8:00 pm
小题5:Which is the best title for the ad.?
A．Wonderful Museum—an Exciting Place for Adults
B．Welcome to Wonderful Museum for a Long Holiday
C．Wonderful Museum—the Best Place to Spend Your Day
D．A Wonderful Tourist Place
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选择题

宣传科学知识，揭露伪科学，是我们的义务．下列各项中属于伪科学的是（　　）

A．用隔水透气的高分子薄膜做的鸟笼，可使鸟在水中生活

B．直径6mm的尼龙绳能吊起质量为2t的汽车

C．我国古代炼丹能“点石成金”

D．医疗上在液氮冷冻麻醉条件下做手术
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