问题 选择题

关于参考系,下列说法正确的是

A.夜晚抬头望月,觉得月亮在云中穿行,选取的参考系是地球

B.太阳从东边升起,从西边落下,选取的参考系是地球

C.乘客看到汽车窗外的景物飞速后退,选取的参考系是汽车

D.人坐船观看两岸青山时,常有"看山恰似走来迎"的感觉,又有"仔细看山山不动"的感觉,选取的参考系都是船

答案

BC

题目分析:夜晚抬头望月,觉得月亮在云中穿行,选取的参考系云,A错误;

太阳从东边升起,从西边落下,选取的参考系是地球,B正确;

乘客看到汽车窗外的景物飞速后退,选取的参考系是汽车,C正确;

人坐船观看两岸青山时,常有“看山恰似走来迎”的感觉,是以船为参考系,“仔细看山山不动”的感觉,是以两岸为参考系的,D错误

故选BC

点评:为了研究和描述物体的运动,我们引入了参考系,选择不同的参考系,同一物体相对于不同的参考系,运动状态可以不同,选取合适的参考系可以使运动的研究简单化.

阅读理解

BROOKSVILLE — It’s the time of year again, when young bears are on their own for the first time. And that means more sightings where bears usually aren’t supposed to be.

This weekend, a 258-pound black bear took a brief tour of Brooksville, with police and firefighters chasing.

Another black bear, weighing just 100 pounds, was spotted Saturday, crossing busy U. S. 19 near a retirement community in Spring Hill. Several other bear reports have come from Citrus County.

"It is really difficult for the younger bears to find their own land around here, " said Niki Everitt, bear hot line director for the Gulf Coast Conservancy.

Brooksville’s bear first was spotted late Thursday crossing State Road 50, headed toward Tom Varn Park. Police and firefighters tracked the bear through the park and the Brooksville Quarry golf course.

The bear then wounded down the middle of Broad Street before being surrounded near Luigi’s Pizza. An official with the Florida Game and Fresh Water Fish Commission came with a tranquilizer spear(加入镇静剂的矛).planning to stick the bear by hand. "The guy saw the size of the bear and figured that wasn’t a great idea, "said Capt. Frank Phillips of the Brooksville Fire Department.

Emergency officials waited until a tranquilizer gun was brought from Land O’ Lakes. The bear then got a free ride to the Chassahowitzka Wildlife Management Area.

It is not unusual for bears to move into living areas this time of year, experts say. Mothers give their male baby bears the boot once the youngsters are 2 years old. With living areas growing, the young bears keep finding smaller and smaller areas in which they can set up their own land.

"They’ re trying to find a land of their own, where they won ‘t get beat up, " said Lt. Rip Stalvey, a game commission spokesman.

Everitt said people should not be too concerned about the recent bear sightings, since" we have never had a bear attack in Florida."

Black bears mainly eat the tender and fresh leaves of Sabal palms, as well as acorns and berries. Recent weeks of dry weather likely have reduced their food supply.

"If we don’t get some relief soon," Everitt said," we’re probably going to see a lot more of it."

1. What’s the main idea of this passage?

A. Bear sightings in living areas worry people.

B. Policemen try hard to get the bears controlled.

C. People take up too much land from bears.

D. ears come out to disturb people’s lives.

2. Which is true according to the passage?

A. The 100-pound bear was caught near Luigi’s Pizza.

B The Gulf Coast Conservancy makes bears homeless.

C. Brooksville’s bear was too large to be caught by hand.

D. Bears frequently visit humans’ living areas.

3. Bear sightings can usually be expected ______.

A. in the cold season                    B. in the warm season

C. near lakes or rivers                   D. near Luigi’s Pizza

4. The underlined phrase "give their male baby bears the boot" means______.

A. make them wear the boots             B. find new homes for them

C. drive them away from home            D. keep them in safe places

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