**Core Concept:** Language processing in the brain, particularly Broca's and Wernicke's areas, and their connections.

**Why the Correct Answer is Right:**
The correct answer, **B** (Broca's aphasia), is derived from the understanding that the patient has difficulty understanding written language but not auditory information. This suggests that the problem lies in the language processing areas of the brain, which are primarily involved in reading and writing.

Broca's aphasia is characterized by difficulty in producing speech and writing, with preserved comprehension of spoken language and reading. The patient's age (70 yr old male) and recent history of head trauma after a fall from stairs are also indicative of this diagnosis, as traumatic brain injury can cause focal lesions in these areas.

**Why Each Wrong Option is Incorrect:**
A. Wernicke's aphasia (difficulty in understanding spoken language without affecting written language) is not applicable in this case because the patient has no difficulty in understanding spoken language.
C. Global aphasia (difficulty in both language production and comprehension) is incorrect because the patient has preserved comprehension of spoken language and reading.
D. Aphasia due to a stroke affecting the whole brain (non-focal aphasia) is not the correct answer because the patient has a focal lesion (head trauma) that specifically affects Broca's area.

**Clinical Pearl:**
Wernicke-Korsakoff syndrome, which is characterized by difficulty understanding spoken language (Wernicke's aphasia) and memory loss (Korsakoff's syndrome), is often associated with thiamine deficiency, particularly in alcoholics. This is not relevant to our patient, as the cause of language impairment is a focal lesion (head trauma) rather than a systemic deficiency. Broca's and Wernicke's areas are essential for language processing, and their dysfunction can lead to the described symptoms.

**Correct Answer Explanation:**

The correct answer, Broca's aphasia (B), is based on the patient's symptoms of difficulty in producing speech and writing, while comprehension of spoken language and reading remain intact. The focal lesion, caused by the recent head trauma, is responsible for this language impairment, specifically affecting Broca's area, which is involved in language production.