题干

静止在粗糙水平面上的物块A受方向始终水平向右的拉力作用下做直线运动,4s时停下,其速度—时间图象如图所示,若物块A与水平面间的动摩擦因数处处相同,则下列判断正确的是(  )

A:全过程拉力做的功等于零

B:全过程中拉力做的功等于物块克服摩擦力做的功

C:从t = 1s到t = 3s这段时间内拉力不做功

D:从t = 1s到t = 3s这段时间内拉力的功率保持不变,该功率为整个过程的最大值

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B

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    Queensland is one of the most amazing states in Australia. It has some of the most beautiful natural scenery on the planet, with the Great Barrier Reef, rainforests and impressive beaches.

The Great Barrier Reef

    It is one of the world's largest natural features. It stretches more that 2,300 km along the north eastern coast of Australia from the northern tip of Queensland to just north of Bundaberg. The things that most surprise visitors to the reef are the colors.

Without doubt, the best way to see the Great Barrier Reef is by diving. If you have a little extra money and you are feeling a bit lazy, you can fly over the reef in a plane.

Fraser Island

    Another area of natural beauty is Fraser Island. This is the world's largest sand island. It's best visited from Hervey Bay on the mainland, where there are a number of places offering trips around the island. To fully appreciate Fraser Island you should go for three or four days. Attractions include some beautiful fresh-water lakes, particularly Lake Wabby and Lake Mckenzie. You can walk around these on white sands untouched by human footprints. Indian Head also has some beautiful views. Braver travelers can go and watch sharks circling the water hundreds of meters below.

The Whitsunday Islands

    It would be a pity to travel around Queensland without taking a trip around the Whitsunday Islands. They were named by Captain Cook in 1770, after the day on which he arrived. Here are some of the great things you can do there.

●Cruise around them on a relaxing trip.

●Take a sailing course.

●Look at the aboriginal (土著的) paintings in caves on Hook Island.

●Have fun in the water doing lots of water sports.

    So, will you be going to Queensland?