题干

引力波是爱因斯坦广义相对论中的重要推论。时间和空间会在质量面前弯曲,时空在伸展和压缩的过程中,会产生振动传播开来,这些振动就是引力波。科学家们花了半个世纪搜寻引力波,直到近期美国科学家才探测到了第一例编号为 GW150914 的引力波,这一发现被称作“上帝的礼物”。这表明(  )

①科学实验活动是检验认识真理性的唯一标准

②世界上只有尚未认识的事物,而没有不能认识的事物

③世界真正统一性在于它的物质性

④人们可以通过实践把观念的存在变为现实的存在

A:①②

B:①④

C:②③

D:③④

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答案(点此获取答案解析)

C

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    Climbing Without Ropes

    The popular image of the mountain climber is of a person carefully climbing a steep cliff with a network of safety ropes, but it is not the only kind. Many climbers now enjoy bouldering. It's more accessible and better for the environment.

What is bouldering?

Bouldering is a sport that involves climbing on, over, and around boulders up to approximately twenty feet above the ground. Participants employ no safety ropes.

Why boulder?

• improve your climbing skills by focusing on basics

• places to climb, such as climbing walls at gyms and parks, easy to find

• less time commitment to bouldering than to mountain climbing

• intellectual and physical enjoyment as one solves problems


Bouldering Terms

crimp: a very small handhold

foothold: a place where one may place a foot to aid in climbing boulder

jug: a very large handhold that is easy to use

problem: The path up a boulder is referred to as the “problem” that one must solve. The “solution” is the sequence of moves one makes up and over a boulder.

    Here is an example of a climber addressing a bouldering problem.

    Figure 1: The climber has two routes she could take, one to the left and one to the right. The left one appears easier because it has a jug within easy reach, but look what happens if she chooses that direction. She gets stuck on the rock and has to go back down. Sometimes that is even more difficult than going up.

    Figure 2: The climber takes the one to the right this time. Using a foothold and placing her right hand in a crimp, she is able to lift herself up and locate other handholds. After only a few moves, she is able to throw her leg over the top of the boulder and pull herself up.