Answer: Option (b) is the correct answer.
Step-by-step explanation:
When two atoms or substances come in contact with each other then they react with one another. As a result, there will be exchange of electrons between them.
For example, when sodium comes in contact with chlorine then it results in the formation of sodium chloride.

Thus, we can conclude that out of the given options, electrons are transferred when objects come into direct contact with each other.