Suppose that Crystal has just finished smoking a cigarette and is thinking about throwing the cigarette butt onto her neighbor Brian's driveway. Although no police officers are around, she instead decides to carry it to a trash can because she doesn't want to embarrass herself by letting people see her littering.

Which of the following types of private solutions to the externality of littering has occurred in this case?

a) Contracts
b) Integration of different types of businesses through merger or acquisition
c) Charities
d) Moral codes and social sanctions

Moral codes refers to acceptable or right ethics that guides people's conducts . Social sanctions refers to actions not necessarily back or enforceable legally that force the people to behave in the right manner.

In the above scenario Brian was not willing to litter the floor due to anticipated public negative reaction s to her littering the floor with cigarettes butt.

It's not a contract for no two parties are involved, nor involved busines merger and neither is it a charity action.