The numerical expression 
shows ([a-z]+)
A Rational numbers are closed under addition.
B Rational numbers are not closed under addition.
C Rational numbers are closed under multiplication.
D Addition of rational numbers is not commutative.
The numerical expression shows ([a-z]+)
A Rational numbers are closed under addition.
B Rational numbers are not closed under addition.
C Rational numbers are closed under multiplication.
D Addition of rational numbers is not commutative.