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【单选题】
SECTION B PASSAGES Directions: In this section, you will hear several passages. Listen to the passages carefully and then answer the questions that follow. 听力原文: (16[C])'We need plenty more seals', Oolak said as they parted. He added, 'But you (15[A])don't shoot seal in water now for they axe hard to get'. Two hours passed, during which Bob had heard Oolak's rifle crack four or five times. (17[A])Boh decided to look for his companion and rejoin him. He climbed an ice pinnacle to look. It was a peaceful scene that met Bob's gaze. White ice stretched before him with little streams flowing across its surface. The low hills and open plains of ice were all bathed in golden sunlight. He did not see Oolak, but he became aware that the dogs had been howling for some time. It dawned on him that the entire team was in an uproar. When he glanced his way to see what the trouble was, his heart almost froze. Walking toward them was an immense whitish form, sleek head hanging low -- a polar bear! The bear smelled a freshly killed seal which Oolak had dragged to the sled, and it was this that he was seeking. To the clamor of the dogs he paid no more attention than if it were the buzzing of a fly. In his entire life the huge beast had never known fear, for the polar bear is the ruler of the ice. He knows no enemies. According to the passage, it is not easy to get seal ______.
A.
in water
B.
on the ice
C.
in the polar region
D.
on the pinnacle
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参考答案:
举一反三
【判断题】离子键是阴、阳离子之间通过静电作用所形成的化学键
A.
正确
B.
错误
【简答题】某输水的水泵系统, 经管路计算得 , 需泵提供的压头为 He=19m 水柱,输水量为 20kg/s ,则泵的有效功率为 _________ 。
【单选题】阴、阳离子间,通过静电作用所形成的化学键为
A.
离子键
B.
非极性共价键
C.
极性共价键
D.
配位键
【简答题】某输水的水泵系统 , 经管路计算得 , 需泵提供的压头为 He=25m 水柱, 输水量为 20kg/s, 则泵的有效功率为 _________.
【单选题】某输水的水泵系统,经管路计算得,需泵提供的压头为He=19[m水柱],输水量为20[kg/s],则泵的有效功率为()瓦.
A.
372.8
B.
37280
C.
3728
D.
37.28
【简答题】某输水的水泵系统,经管路计算得,需泵提供的压头为H=19 m水柱,输水量为20kg/s,则泵的有效功率为____W。(g取9.8)
【简答题】某输水的水泵系统,经管路计算得,需泵提供的压头为H = 19m水柱,输水量为20kg·s -1 ,则泵的有效功率为____
【简答题】某输水的水泵系统 , 经管路计算得 , 需泵提供的压头为 He=25m 水柱 , 输水量为 0.0079 m 3 /s , 则泵的有效功率为 ________.
【判断题】离子键是阴、阳离子之间通过静电作用所形成的化学键
A.
正确
B.
错误
【简答题】某输水的水泵系统,经管路计算得,需泵提供的压头为He=19m水柱,输水量为0.0079m 3 /s,则泵的有效功率为()。
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