截止閥的作用有() ①截止或接通 ②調(diào)節(jié)流量 ③阻止逆向流動
A.① B.② C.①② D.①②③
A.7.5°/10° B.22.5°/10° C.10°/15° D.15°/10°
A.7°/10° B.10°/5° C.10°/15° D.15°/10°