甲升降机比乙升降机的机械效率高，它们分别把相同质量的物体匀速提升相同的高度。则
| A．乙升降机提升重物做的有用功较多 |
| B．甲升降机的电动机做的额外功较多 |
| C．甲升降机的电动机做的总功较少 |
| D．乙升降机的电动机做的总功较少 |
如图所示，一把太阳伞固定在地面上，一阵大风吹来，伞面被“吸”，严重变形。下列有关这一现象及其解释，正确的是
| A．伞面被向下“吸’’，伞上方的空气流速大于下方 |
| B．伞面被向上“吸”，伞上方的空气流速大于下方 |
| C．伞面被向下“吸”，伞上方的空气流速小于下方 |
| D．伞面被向上“吸”，伞上方的空气流速小于下方 |
下图表示四冲程内燃机工作时各冲程的示意图，它们正确的排列顺序为
| A．甲、乙、丙、丁 | B．丁、丙、乙、甲 |
| C．甲、丙、乙、丁 | D．甲、丁、乙、丙 |
如图所示的电路中，R1、R2均为定值电阻，电源电压不变，闭合开关S1、S2，两电表均有示数。若断开开关S2，则
| A．电流表的示数变大，电压表的示数变小 |
| B．电流表的示数变小，电压表的示数变大 |
| C．电流表和电压表的示数都变小 |
| D．电流表和电压表的示数都变大 |
There was a boy who was sent by his parents to a boarding school (寄宿学校). 36 being sent away, this boy was the 37 student in his class. He was at the top in every 38 always with high marks.
But the boy changed after 39 home and attending the boarding school. His grades started 40 . He hated being in a 41 . He was lonely all the time. And there were especially dark times when he 42 committing suicide (自杀). All of this was because he felt 43 and no one loved him.
His parents started 44 about the boy. But they even did not know what was 45 with him. So his dad decided to travel to the boarding school and 46 him.
They sat on the bank of the lake near the school. The father started asking him some casual questions about his classes, teachers and 47 . After some time his dad said, “Do you know, son, why I am here today?”
The boy answered back, “To 48 my grades?”
“No, no,” his dad replied. “I am here to tell you that you are the most 49 person for me. I want to see you 50 . I don’t care about grades. I care about you. I care about your happiness. YOU ARE MY LIFE.”
These words 51 the boy’s eyes to be filled with tears. He 52 his dad. They didn’t say anything to each other for a long time.
Now the boy had 53 he wanted. He knew there was someone on this earth who cared for him deeply. He 54 the world to someone. And today this young man is in college at the top of his class and no one has ever seen him 55 !
But the boy changed after 39 home and attending the boarding school. His grades started 40 . He hated being in a 41 . He was lonely all the time. And there were especially dark times when he 42 committing suicide (自杀). All of this was because he felt 43 and no one loved him.
His parents started 44 about the boy. But they even did not know what was 45 with him. So his dad decided to travel to the boarding school and 46 him.
They sat on the bank of the lake near the school. The father started asking him some casual questions about his classes, teachers and 47 . After some time his dad said, “Do you know, son, why I am here today?”
The boy answered back, “To 48 my grades?”
“No, no,” his dad replied. “I am here to tell you that you are the most 49 person for me. I want to see you 50 . I don’t care about grades. I care about you. I care about your happiness. YOU ARE MY LIFE.”
These words 51 the boy’s eyes to be filled with tears. He 52 his dad. They didn’t say anything to each other for a long time.
Now the boy had 53 he wanted. He knew there was someone on this earth who cared for him deeply. He 54 the world to someone. And today this young man is in college at the top of his class and no one has ever seen him 55 !
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对下列四幅图阐述合理的是
0 65725 65733 65739 65743 65749 65751 65755 65761 65763 65769 65775 65779 65781 65785 65791 65793 65799 65803 65805 65809 65811 65815 65817 65819 65820 65821 65823 65824 65825 65827 65829 65833 65835 65839 65841 65845 65851 65853 65859 65863 65865 65869 65875 65881 65883 65889 65893 65895 65901 65905 65911 65919 235360
| A．A图：磁场能产生电流 |
| B．B图：闭合开关，通电导体在磁场中受到力 |
| C．C图：闭合开关，导体棒在磁场中受到力 |
| D．D图：微波炉利用电流的热效应工作 |
