The correct answer is option (C):
Despite his age his skill in tennis
The original sentence is: Despite his age his skill at tennis is good.
The underlined part is "at tennis". We need to find the best replacement from the given options.
Let's analyze the options:
Option 1: Despite of his age his tennis
"Despite of" is grammatically incorrect. The correct idiom is "despite" or "in spite of". Also, "his tennis" is too general and doesn't specify what about his tennis is good.
Option 2: Despite his age his skill of tennis
While "skill of tennis" might be understandable, the more common and natural preposition to use with "skill" when referring to a particular activity or subject is "in". For example, we say someone has a "skill in programming" or a "skill in painting".
Option 3: Despite his age his skill in tennis
This option uses the correct preposition "in" with "skill" to indicate proficiency in the activity of tennis. This is the standard and most idiomatic way to express this idea. The sentence reads: "Despite his age, his skill in tennis is good." This is grammatically sound and clearly conveys the intended meaning.
Option 4: No change
As discussed, while "at tennis" is not strictly incorrect, "in tennis" is generally preferred when referring to skill or proficiency in a sport or activity. "Skill at" can sometimes imply the ability to perform a specific action within that activity, whereas "skill in" refers to a broader mastery or expertise. In this context, "skill in tennis" is a more common and natural phrasing.
Therefore, replacing "at tennis" with "in tennis" improves the sentence's idiomatic correctness and natural flow.