When does auxiliary burner of incinerator put into operation? （） Ⅰ.tart incinerator when it is cold Ⅱ.he sludge for dealing with is little Ⅲ.he sludge for dealing with is large Ⅳ.he water and impurity in sludge are too much Ⅴ.he temperature in incinerator is low Ⅵ.ealing with little solid rubbish