The five is after the decimal point. The 10 in that form is tenths. It represents a number in the denominator. So you would write it as 5/10 and say it as 5 tenths.
It's definitely not A. five ones, or C. five tens, since the 5 is behind the decimal. It's not B. five hundredths either, because that would be the value behind 5 in the tenth place.
