可吸入性纤维粉尘是指（）

A.直径>31μm，长度<5μm

B.直径>3μm，长度≥5μm

C.直径<3μm，长度<5μm

D.直径<3μm，长度≥5μm

E.直径<3μm，长度≥91μm

Halon fire extinguishers are NOT effective when used on which types of fires?（）

A.Fires in electrical equipment

B.Flammable oils and greases

C.Class A fires in ordinary combustibles

D.Materials containing their own oxygen