【单选题】

(78)Professor Martin’s report says that children who attend a number of different schools, because their parents have to move around the country, probably make slow progress in their studies. There are also signs, says Professor Martin, that an unusually large number of such children are mentally (精神上) affecteD、

The professor says, "It’s true. My personal feeling is that children should stay in one school. However, our findings are based on research and not on any personal feelings that I or my assistants may have on the subject."
Captain Thomas James, anArmy lecturer for the past 20 years and himself a father of two, said, "I’ve never heard such rubbish. Taking me for example, no harm is done to the education of my children who change schools regularly---if they keep to the same system(系统) ,as in ourArmy schools. In my experienceArmy children--and I’ve known quite a few of them--are as well - adjusted(善于适应的)as any others, if not more so. What the Professor doesn’t appear to appreciate is the fact that in such situations children will adapt(适应)much better than grown - ups."
When this was put to Professor Martin, he said that at no time had his team suggested that all such children were backward or mentally affected in some way, but simply that in their experience there was a clear tendency (趋向).
"Our findings show that while the very bright child can deal with regular changes without harming his or her general progress in studies, the majority of children suffer from constantly having to enter a new learning situation.\
According to Professor Martin’s report, ______.A．children have to go to different schools because of their parents’ moving around
B．children make slow progress because they are mentally affected
C．signs are shown that many children are mentally affected by their studies
D．changing from one school to another too often has ill effect on children’s studies