题干

某高山动物的毛色有深灰色、银灰色和白色,依次受B、by和b基因的控制,研究发现:深灰色个体的毛色会随着季节的变化而改变颜色;对深灰色个体身体的某一部位用一定剂量的紫外线处理后,部分个体的该部位长出白色且毛色不再改变.下列分析错误的是(    )

A:深灰色个体毛色的季节性变化是一种适应现象

B:毛色的季节性变化表明基因的表达受环境条件的影响

C:紫外线引起深灰色个体毛色的改变是突变的结果

D:紫外线能引起B、by和b基因结构的定向改变

上一题 下一题 0.0难度 选择题 更新时间:2017-09-06 01:36:08

答案(点此获取答案解析)

D

同类题2

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    How to Say Goodbye

    Knowing how and when to say goodbye is often difficult, even in informal situations. But learning to say goodbye appropriately is a skill that will help you keep your relationships and let people know you care.____ Read on to learn how to recognize opportunities when you leave.

    ____

    When you're at any kind of party or gathering, or even a one-on-one conversation, it can be difficult to get away. Learning to recognize good opportunities to leave will make a short-term goodbye much easier.

Watch body language.

    People don't like telling you that they'd like you to leave.____ If the host of a party starts cleaning up, or withdraws (退出) from the conversation, gather your friends or belongings and make your exit. If someone starts checking their watch, or seems otherwise restless, it's also time to leave.

    Make plans to see each other again.

    Even saying, “See you at school tomorrow,” or “Can't wait to see you again at Christmas” keeps the goodbye light and focused forward.____

Tell the truth.

    Many people expect to come up with a “good excuse” when they're ready to leave.____If you want to leave, just say, “I'm going to go now, see you later.”

A. You don't need to.

B. Set up a coffee date.

C. Recognize when to leave.

D. So try and watch for signals.

E. It makes the goodbye easier.

F. It's also easier than it seems sometimes.

G. If you haven't already made plans, use it as an opportunity to make them.