痕量气体trace: n. (马车等的)挽绳,挽车的皮带;【机械工程】连动杆; ...gas: GAS = gasoline. gases: 气体a trace: a扫迹; a扫描轨迹; 踪迹a-trace: 扫描线下载手机词典可随时随地查词查翻译