Chemistry MCQ help!

So pretty simple question. Why the product in A does not form but the product in B does?

A cannot be the product because bromine is a stronger electrophile than chlorine, so bromine will have to attack the double bond first, resulting in the formation of a carbocation next to the carbon where the first bromine was attached. And then, chlorine or bromine can get attached to the carbocation formed. So B and C are the only possible answers.

So on what basis do we rank electrophiles? What factors decide which ion/molecule is a better electrophile?
And thanks a lot for your reply !