题干

下列有关内环境及其稳态的叙述中,正确的是(    )

A:内环境由细胞内液和细胞外液组成

B:内环境是细胞与外界环境进行物质交换的媒介

C:外环境的变化一定会破坏内环境的稳态

D:正常情况下内环境的各项理化性质恒定不变

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答案(点此获取答案解析)

B

同类题3

根据短文理解,选择正确答案。

    Each time I see a balloon, my mind flies back to a memory of when I was a six-year-old girl. It was a rainy Sunday and my father had recently died. I asked my mom if Dad had gone to heaven. "Yes, honey. Of course." she said.

    "Can we write him a letter?"

    She paused, the longest pause of my short life, and answered, "Yes."

    My heart jumped. "How? Does the mailman go there?" I asked.

    "No, but I have an idea." Mom drove to a party store and returned with a red balloon. I asked her what it was for.

    "Just wait, honey. You'll see." Mom told me to write my letter. Eagerly, I got my favorite pen, and poured out my six-year-old heart in the form of blue ink. I wrote about my day, what I learned at school, how Mom was doing, and even about what happened in a story I had read. For a few minutes it was as if Dad were still alive. I gave the letter to Mom. She read it over, and a smile crossed her face.

    She made a hole in the corner of the letter where she looped the balloon string. We went outside and she gave me the balloon. It was still raining.

    "Okay, on the count of three, let go. One, two, three."

    The balloon, carrying my letter, darted upward against the rain. We watched until it was swallowed by the mass of clouds.

    Later I realized, like the balloon, that Dad had never let his sickness get him down. He was strong. No matter what he suffered, he'd persevere, hang on, and finally transcend this cold world and his sick body. He rose into sky and became something beautiful. I watched until the balloon disappeared into the gray and white and I prayed that his strength was hereditary. I prayed to be a balloon.