<em> Proactive interference</em> happens when previously learned material gets in the way of learning something new. When you are trying to learn new pieces of information, old memories continously pop up, making it hard to remember the new ones. For instance, you are trying to learn and then recall the new address of your best friend and the old one keeps popping up, making it difficult to remember the new one.
Answer B is the correct answer. Ken studied French history in the past. Some facts of what he already knows about Marie Antoinette are different from what he is learning now and it seems his previous knowledge gets in the way. Now there's new pieces of information he needs to learn about Marie Antoinette but he finds it hard to grasp those new discoveries.
