题干

弹簧测力计是科学实验中常用的仪器.下列关于其它的说法中不正确的是(  )

A:称量物体前首先应估计被测力的大小,以免超过量程

B:称量前,要轻轻拉动几下弹簧,这是为了避免弹簧卡在外壳上

C:只要弹簧不断,可以朝任意方向拉动弹簧测力计

D:弹簧测力计的工作原理是在弹簧的弹性限度内,弹簧的伸长与受到的拉力成正比

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C

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    Natural sites and historic buildings,when left alone,can slowly be in bad condition.____For these reasons we must protect them.

    “World Heritage" is the title given to places chosen from natural sites and buildings around the world. These places are considered special,valuable and require protection. They may be places of nature or cultural heritages that are the pride of the people in the country____ Each is a treasure of our planet that must be protected for us and our future generations.

    Even extremely beautiful natural environments can be in bad condition if they are left alone____For instance,the Galapagos Islands are now protected by rules that stop people from bringing or removing plants and animals to or from the islands, moving rocks and touching the animals. In the US,people are not allowed to visit Grand Canyon National Park by vehicle. It aims to protect the park's environment from the gas produced by cars____ Australia is making stricter laws to prevent agricultural chemicals from flowing into the ocean near the Great Barrier Reef. Efforts are also being made to protect Natural Heritage sites in Japan. In Shiretoko,only a small number of people are allowed to walk on its nature path at the same time____

A. They may also be home to endangered species(物种).

B. Today there are 183 Natural Heritage sites around the world.

C. People can change these places too,just as the wind and rain can.

D. Natural Heritage is valued for geographical characteristics and beautiful scenery.

E. That's why measures are being taken around the world to protect them.

F. It can reduce the risk of people accidentally stepping on valuable plants.

G. There are even security guards there who can arrest people that break the rules.