题干

感染赤霉菌而患恶苗病的水稻植株,要比周围的健康植株高50%以上,患病植株结实率很低;将赤霉菌培养基的滤液喷施到水稻幼苗上,没有感染赤霉菌的幼苗也表现出恶苗病的症状;从赤霉菌培养基中提取出有以上效应的活性物质――赤霉素.通过上述实验得出的结论不正确的是:

A:赤霉素是植物激素

B:使水稻患恶苗病的是赤霉菌的代谢产物,不是赤霉菌本身

C:赤霉菌产生的物质使水稻患恶苗病

D:上述实验还不能证明赤霉素是植物激素

上一题 下一题 0.0难度 选择题 更新时间:2018-04-16 12:03:29

答案(点此获取答案解析)

A

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。

    For college students, graduation signals an exciting new beginning. ____ Many students wonder: What do I do now? What career is best for me? Most expert advice on choosing careers boils down to the following points.

Knowing Yourself

    What are your interests? Abilities? Skills? ____ The results may surprise you! These can be useful, but they're not the last word.

Investigating

    Investigating occupations is much more difficult. For most people, there isn't just one ‘right' job, but several that could be satisfying. ____ Talk to people who have occupations that interest you. Find out what they like and dislike about their job.

____

    Many people choose their careers because they believe strongly in a particular cause. Some might choose to work in areas like medicine, charity or environmental protection. Some have a strong interest in history or a love for the arts. ____ So in cases like these, the field is often chosen first, rather than the occupation itself. So if you've chosen a field, self-assessment will help you find your place in it. Invest some time and effort, and find the right career for you.

A. Try a self-assessment quiz.

B. Search through books and Web sites.

C. Finding your place.

D. But it can also bring a lot of uncertainty and confusion.

E. Serious research helps narrow the possibilities

F. Research your chosen field carefully. What work needs to be done? What training is needed?

G. Then they might think about education, museums or art production.