The correct option is D 737
The combination of a whole number and a proper fraction is called a mixed fraction.
Here,
323=3+23 ; where 3 is a whole number and 23 is a proper fraction.
737=7+37 ; where 7 is a whole number and 37 is a proper fraction.
323 and 737 are combination of a whole number and a proper fraction.
So, 323 and 737 are mixed fractions.