题干

用电子显微镜观察根毛细胞,下列各组结构均不能观察到的是(    )

A:液泡和中心体

B:高尔基体和核糖体

C:叶绿体和中心体

D:液泡和内质网

上一题 下一题 0.0难度 选择题 更新时间:2020-03-31 07:18:44

答案(点此获取答案解析)

C

同类题5

完形填空。阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项。

    On that particular day after I finished giving my training course, I took a flight home. Upon 1 the plane, I noticed a boy who was around eight years old, sitting in the window seat 2 mine. Trying my best to be 3, I said “hello” and introduced myself, and he told me his name was Bradley. We started a 4 and within minutes, he took me into his confidence, saying, “This is the first time I have ever been on a plane. I'm a little bit 5.” I managed to 6 him.

    As we ascended (上升), he looked out of the window and started describing excitedly everything he was 7. Then he told me he needed to go to the bathroom, 8 I stood up to let him out into the aisle. It was then that I noticed the brace (支柱) on his legs. Bradley, 9 made his way down to the bathroom and back. Sitting back down, he 10, “I have muscular dystrophy(肌肉萎缩症), and so does my sister, who's in a 11 now.”

    As we descended (下降), he looked over, smiled, and spoke in a low, almost 12 voice, “You know, I was really 13 about who would sit beside me on the plane. I was afraid it would be someone who didn't want to 14 with me. I'm so 15 I sat beside you.”

    16 the whole experience later that night, I was reminded of the 17 of being open to the moment. Now when 18get(s) rough, I look out of the window, try to see what images the clouds are painting in the sky, 19 remember Bradley, the beautiful child who taught me that 20.