Correct option is A
The incorrect part is (A).
Detailed Analysis
- The Error: "Despite of"
- The Rule: The word "Despite" is a preposition that functions on its own. It is never followed by the word "of." This is a frequent mistake caused by confusing it with the phrase "In spite of," which carries the exact same meaning but does require the "of."
- The Correction: Change it to either "Despite" or "In spite of."
Breakdown of Other Parts
- (B) his busy schedule: Correct. A standard noun phrase acting as the object of the preposition.
- (C) he manages to: Correct. The singular subject "he" matches the singular verb "manages."
- (D) spend time with his family: Correct. "Manage to" is correctly followed by the base verb "spend."
Comparison: Despite vs. In Spite Of
Both expressions are used to show contrast, but they cannot be mixed.