Final answer:
The patient exhibiting difficulty remembering past events before being hit by a baseball is experiencing retrograde amnesia, which is characterized by the loss of memory for events that happened prior to the injury.
Step-by-step explanation:
If a patient is having trouble remembering events prior to being struck in the head by a baseball, they are experiencing retrograde amnesia. Retrograde amnesia involves the loss of memory for events that occurred before the injury, meaning that one's past memories are inaccessible.
Unlike retrograde amnesia, anterograde amnesia refers to the inability to form new memories after the trauma, which is not the case described by the patient. Therefore, the correct answer to the question is B. retrograde amnesia. This condition typically affects episodic memories, which are autobiographical in nature, but it doesn't necessarily impede the ability to form new procedural memories.