问题 选择题

在酵母菌培养液中,许多酵母菌细胞上还连接着一个或多个小细胞,这是酵母菌正在进行(    )

A.有性生殖

B.出芽生殖

C.营养生殖

D.嫁接

答案

答案:B

题目分析:酵母菌是出芽生殖,即芽殖是酵母菌最常见的繁殖方式,在良好的营养和生长条件下,酵母生长迅速,这时,可以看到所有细胞上都长有芽体,而且在芽体上还可形成新的芽体,所以经常可以见到呈簇状的细胞团,从母细胞上长出一个芽,逐渐长到成熟大小后与母体分离,在营养状况不好时,一些可进行有性生殖的酵母会形成孢子(一般是四个),在条件适合时再萌发,故选B。

单项选择题

Everyone becomes a little more forgetful as they get older, but men’s minds decline more than women’s, according to the results of a worldwide survey.

Certain differences seem to be inherent in male and female brains: Men are better at maintaining and dealing with mental images (useful in mathematical reasoning and spatial skills), while women tend to excel (擅长) at recalling information from their brain’s files ( helpful with language skills and remembering the locations of objects).

Many studies have looked for a connection between sex and the amount of mental decline (衰退) people experience as they age, but the results have been mixed.

Some studies found more age-related decline in men than in women, while others saw the opposite or even no relationship at all between sex and mental decline. Those results could be improper because the studies involved older people, and women live longer than men: The men tested are the survivors, "so they’re the ones that may not have shown such cognitive decline," said study team leader Elizabeth of the University of Warwick in England.

People surveyed completed four tasks that tested sex-related cognitive skills : matching an object to its rotated form, matching lines shown from the same angle, typing as many words in a particular category (范畴) as possible in the given time, e.g. "object usually colored gray", and recalling the location of objects in a line drawing. The first two were tasks at which men usually excel; the latter were typically dominated by women.

Within each age group studied, men and women performed better in their separate categories on average. And though performance declined with age for both genders, women showed obviously less decline than men overall.

The underlined word in the second paragraph means ().

A.natural

B.great

C.obvious

D.absolute

多项选择题