题干

菠菜根的分生区细胞不断分裂使根向远处生长,在分裂过程中不会出现的是(  )

A:细胞分裂间期,中心体的两个中心粒各自产生一个新的中心粒

B:细胞分裂中期,染色体形态较固定、数目较清晰

C:细胞分裂前期,核膜和核仁逐渐消失

D:细胞分裂末期,高尔基体参与细胞壁的形成

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答案(点此获取答案解析)

A

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    Crying is the sign of the rawest of human emotions. We cry when we can't hold inside what we feel any more. We cry when we're at our best, and when we're at our worst. I mean all of us, men included.

    But we never see other men cry. In no western culture has it ever been acceptable for men to shed(流泪)more than a single tear, and even then it's reserved for grand victories, defeats and deaths. Dutch research suggests that women cry between three and five times more than men. Generally men and women cry over the same things—deaths, break-ups and homesickness, primarily, but researchers believe that men cry more often than women when it comes to positive events.

    I want to admit I'm a bit of a cryer. However, having never really experienced deaths in my life, a few weeks ago I experienced what it means to really, truly, pour my heart out in tears.

    See, my dog was killed by a car right outside my house. Being a witness to this painful event left me in shock for a good hour, but then the floodgates opened. Over the next 48 hours, I might have cried 20 times. Once or twice I crouched(蹲)on the floor with my head in my hands and tears were the only outlet.

    It is suggested in the book Adult Crying: A Biopsychosocial Approach that there's certain pleasure in crying. It helps ease stress when there is no other way to express ourselves.

    In those days after my dog's death, I remember thinking, “I've got to stop this crying”. It felt unmanly. It felt like a sign of weakness. I've since realized that tears are for everybody. They show we have sympathy, allow us to get rid of stress and just feel.