He collects （） of all kinds of rocks and minerals.

A. tell parents to pay more attention to the guidance of teachers in the matter of educational activities in the home
B. help ensure that every child’s capacities can fully develop when he leaves school
C. urge teachers and school administrators to make use of a much underused resource of the parents
D. improve the teaching approach in mathematics in and outside the classroom

A. The Effect of Migration on the Regional Economies of the United States Following the First World War.
B. The Reasons for the Subsequent Economic Difficulties of Those Who Participated in the Great Migration.
C. The Transition for the Subsequent Economic Difficulties of Those Who Participated in the Great Migration.
D. The Transition of the Agricultural South Following the Boll-weevil Infestation.