"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 =Â $$\frac{4!}{2!\times2!}=6$$
2. Two of the letters are either "O" or "R" and the others are distinct.
The total number of arrangements =Â $$^2C_1\times^8C_2\times\frac{4!}{2!}=2\times28\times12=672$$
3. All four letters are distinct.
The total number of arrangements =Â $$^9C_4\times4!=3024$$
Thus, the total number of four-letter words possible = $$6+672+3024=3702$$.
Hence, the answer is option C.
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