有效成分（Effective Constituents）

1、Roman control was only effective in（）.

Roman control was only effective in（）.AScotlandBWalesCLondonDThe southeast of Britai

2、Firefighting foam is only effective wh

Firefighting foam is only effective when the foam（）.Apenetrates to the bottom of the fireBis kept saturated with low-velocity water fogCmixes with the burning fuel oilDcompletely covers the top of the burning liquid

3、线路有效长 effective length of track

线路有效长 effective length of track

4、The most effective first aid treatment

The most effective first aid treatment for chemical burns is to immediately（）.Aapply ointment to the burned areaBflood the affected area with waterCwrap the burn with sterile dressingDapply an ice pack to the burned area

5、An effective braking system for windla

An effective braking system for windlasses on rigs in deep water is a(n)（）.Alarger chain stopperBdisc backstopping brakeChydraulic clutchDelectrical regenerative braking system

6、An extinguishing agent which effective

An extinguishing agent which effectively cools，dilutes combustible vapors，removes oxygen，and provides a heat and smoke screen is（）.Acarbon dioxideBHalon 1301Cdry chemicalDwater fog