In a workshop, if you are looking for a fire extinguisher, the most effective choice from the options provided would be:
A. Bucket filled with sand
Additionally, though not typically preferred for all types of fires, a bucket filled with water (B) can be used for certain types of fires (such as Class A fires involving ordinary combustibles). However, it is important to note that water should not be used on all types of fires, especially Class B (flammable liquids) and Class C (electrical) fires.
The other options are not suitable for extinguishing fires:
C. Green leaves - not effective for extinguishing fires. D. Jerry can of oil engine - highly flammable and dangerous. E. Wet sand dust - without being specifically formulated for fire suppression, wet sand may not be reliable.
Therefore, the best option is A. Bucket filled with sand.