气体灭火系统管道可采用螺纹连接、法兰连接或焊接，公称直径等于或小于80mm的管道，宜选用螺纹连接；公称直径大于80mm的管道，宜采用法兰连接。
1、正确正确
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Someconceptsmaybedifficulttograspchieflybecausetheymaybeunfamiliaror_____ideas,opinionswhichwealreadyhold.
Peopleinsomeareasdon’thavetopayfortheir______.
Hebuiltatelescope____hecouldstudytheskiesinhisfreetime.
Thelittleboydidn’tknow_______.
I’dliketohavealongholiday,butI’mreallytoobusyto_____thetime.
