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Explanation:

"CORONAVIRUS" has 7 distinct alphabets and two pairs of repeated characters ", O" and "R".
There are three possible cases for creating 4 letter words.
1. Two letters are "O" and the other two are "R".
The total number of arrangements = $\frac{4!}{2!\times 2!}$ = 6
2. Two of the letters are either "O" or "R" and the others are distinct.
The total number of arrangements = ²C₁ × ⁸C₂ × $\frac{4!}{2!}$ = 2 × 28 × 12 = 672
3. All four letters are distinct.
The total number of arrangements = ⁶C₄ × 4! = 3024
Thus, the total number of four-letter words possible = 6 + 672 + 3024 = 3702.
Hence, the answer is option C.