Let us match each function with the correct category.
ROUND() is a math function because it rounds numeric values.
COUNT() is an aggregate function because it counts rows or non-null values.
YEAR() is a date function because it extracts the year part from a date value.
RIGHT() is a text function because it extracts characters from the right side of a string.
So the correct matching is: (i)-(b), (ii)-(a), (iii)-(d), (iv)-(c).
Therefore, the correct option is (B).