慢性、反复发作并呈节律性上腹疼痛是E．

A. 插入排序
B. 选择排序
C. 快速排序
D. 归并排序

A. white Americans would not give their blood
B. black Americans were unwilling to give their blood
C. no one was able to give his blood
D. both the white and the black gave blood