—How long has the nationwide ban (禁止) on plastic bags been put into practice?

— _______ the beginning of June. [ ]

A. Behind

B. Since

C. Among

D. At

纪律审查人员必须严格按照规定程序开展纪律审查工作。包括（）

A.要严格遵守廉洁自律准则

B.要严格遵守请示报告制度

C.要严守保密纪律

D.要实行严格的回避制度