Electrophilic reagents are

 

A reagent is a substance that reacts in a chemical reaction. It's called a reagent because it's the first participant in the reaction, as opposed to products or catalysts which come later. 

Just as reagents are necessary for reactions to take place, electron donors must be available for electron transfer (or redox) reactions to occur, and so are also reagents. Examples of electrophiles include free radicals and ions containing halogens.

Electrophilic reagents are things that love electrons. Because of this, they attack those things which need extra electrons to be stable. Electrophiles don't always need a whole extra electron, but a partial charge is good enough for them to want to react.

Hence, option B is correct.