【单选题】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 al...
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