单项选择题
A.turning gear B.motor C.driving gear D.driven gear
Energy losses due to （） occur in every machine.A.speedB...
单项选择题Energy losses due to （） occur in every machine.
A.speed B.friction C.impact D.atmosphere
Emulsion oils and sodium nitrite are both approved addi...
单项选择题Emulsion oils and sodium nitrite are both approved additives, but （） cannot be used if any pipes are galvanized or if soldered joints exist.
A.the latter B.latter C.former D.the former
单项选择题Emulsion oils and sodium nitrite are both approved additives, but the latter cannot be used if any pipes are （） or if any soldered joints exit.
A.chromed B.welded C.galvanized D.bolted
