请协助我们，保持地铁清洁卫生。的英文

help us to keep the tube litter free

• 请:    request; ask
• 协助:    assist; help; give ...
• 我们:    we
• 保持:    keep; hold; retain ...
• 地铁:    metro; the subway; ...
• 清洁:    cleaning; clean
• 卫生:    hygienism; hygiene ...