The company installs security systems in nonresidential buildings.公司在非住宅楼里安装了安全保障系统。The government invited tenders for a project to computerize the social security system.政府就社会保障系统计算机化项目进行了招标。There was a problem with the submarine's life-support system.这艘潜艇的生命保障系统出现了问题。