China and the United States held their first strategic dialogue on August 1 and to increa

问题补充：

China and the United States held their first strategic dialogue on August 1 and to increase co-operation and constructive relations.

A. agreed

B. would agree

C. have agreed

D. had agreed

答案：

(答案→)A. agreed

B. would agree

C. have agreed

D. had agreed

解析：因为有确定的过去时间on August 1，再考虑and连接的并列句应时态一致，所以选A。