题干

如图所示,大河的两岸笔直且平行,现保持快艇船头始终垂直河岸从岸边某处开始先匀加速而后匀速驶向对岸,在快艇离对岸还有一段距离时开始减速,最后安全靠岸.若河水以稳定的速度沿平行河岸方向流动,且整个河流中水的流速处处相等,则快艇实际运动的轨迹可能是图中的(   )

A:①

B:②

C:③

D:④

上一题 下一题 0.0难度 选择题 更新时间:2018-02-05 05:37:50

答案(点此获取答案解析)

D

同类题4

完形填空

    I believe in miracles(奇迹) because I've seen so many of them. One day, a patient was referred to me who was one hundred and two years old. 'there's a1in my upper jaw, " she said. "I told my own dentist it's nothing, but he 2I come to see you."

    Her eighty-year-old son accompanied her. He would3to add something, but she stopped him. She wanted to tell everything herself. I found a large cancer that spread over much of the4of her mouth. A careful examination later5that it was a particularly bad sort of cancer. During her next appointment, I explained to her the6of the problem. She clasped my hand in hers and said, "I know you're worried about me, but I'm just7."

    I thought otherwise(不同). After considerable8on my part, and kindness on her part because she wanted to9me, she agreed to have me refer her to a cancer surgeon. She saw him, but as I expected,10  treatment. About six months later she returned to my office, still energetic and11.

    “How are you?” I asked.

    “I'm just fine, honey, ” she responded12 high spirits. “When can I get started on fixing my dentures(假牙)?”

    Surprised to see her at all, I answered13, “Let me take a look in your mouth and we'll see about it.”

    I couldn't believe my eyes. The cancer that had14nearly the entire roof of her mouth was gone-only one small area of redness 15.

    I had read of such things happening, but had16seen them with my own eyes. That was my first miracle. Since then I've seen many others, because they keep getting17to see. In fact, miracles are daily events for me now. And people are a miracle,18through them we have a chance to know ourselves and to19the miracles of one another.

    Since my first miracle, I've come to understand that the place for a miracle is20we choose to find it.