Answer: The answer is A, It was paid for by Reagan-Bush campaign funds.
Explanation: First of all, a Bias is basically an inclination or prejudice towards something in particular. Said inclination can be considered as unfair because it is rather a predisposition rather than an objective opinion.
This add shows bias because it was created by the same campaign the add is promoting (Reagan-Bush). Which means that there is an inclination towards said campaign.