【单选题】

Seven years ago, a group of female scientists at the Massachusetts Institute of Technology produced a piece of research showing that senior women professors in the institute’s school of science had lower salaries and received fewer resources for research than their male counterparts diD、Discrimination against female scientists has cropped up elsewhere. One study—conducted in Sweden, of all places—showed that female medical-research scientists had to be twice as good as men to win research grants. These pieces of work, though, were relatively small-scale. Now, a much larger study has found that discrimination plays a role in the pay gap between male and female scientists atBritish universities.

SaraConnolly, a researcher at the University ofEastAnglia’s school of economics, has been analyzing the results of a survey of over 7,000 scientists and she has just presented her findings at this year’s meeting of theBritishAssociation for theAdvancement of Science in Norwich. She found that the average pay gap between male and female academics working in science, engineering and technology is around ￡ 1,500 ($2,850) a year.
That is not, of course, irrefutable proof of discrimination.An alternative hypothesis is that the courses of men’s and women’s lives mean the gap is caused by something else; women taking "career breaks" to have children, for example, and thus rising more slowly through the hierarchy. Unfortunately for that idea,Dr.Connolly found that men are also likely to earn more within any given grade of the hierarchy. Male professors, for example, earn over ￡ 4,000 a year more than female ones.
To prove the point beyond doubt,Dr.Connolly worked out how much of the overall pay differential was explained by differences such as seniority, experience and age, and how much was unexplained, and therefore suggestive of discrimination.Explicable differences amounted to 77% of the overall pay gap between the sexes. That still left a substantial 23% gap in pay, whichDr.Connolly attributes to discrimination.
Besides pay, her study also looked at the " glass-ceiling" effect—namely that at all stages of a woman’s career she is less likely than her male colleagues to be promoteD、Between postdoctoral and lecturer level, men are more likely to be promoted than women are, by a factor of between 1.04 and 2.45. Such differences are bigger at higher grades, with the hardest move of all being for a woman to settle into a professorial chair.
Of course, it might be that, at each grade, men do more work than women, to make themselves more eligible for promotion.But that explanation, too, seems to be wrong. Unlike the previous studies,Dr.Connolly’s compared the experience of scientists in universities with that of those in other sorts of laboratory. It turns out that female academic researchers face more barriers to promotion, and have a wider gap between their pay and that of their male counterparts, than do their sisters in industry or research institutes independent of universities. Private enterprise, in other words, delivers more equality than the supposedly egalitarian world of academia does.
The phrase "cropped up" in the first paragraph most probably means______.
A、plantedB、thrivedC、elevatedD、happened