简述社会体育的基本特点？

A. 正确
B. 错误

A. 户口簿、身份证
B. 门诊处方、就医发票
C. 合疗本、就医发票
D. 门诊处方、户口簿

A. opposed-piston engine
B. double-acting engine
C. two-stroke/cycle engine
D. four-stroke/cycle engine