The proper fraction is c. 9/10.
A proper fraction is a fraction where the numerator (top number) is less than the denominator (bottom number).
a. 11/11 is not a proper fraction because the numerator and denominator are equal, making it an improper fraction that can be simplified to "1."
b. 4/1 is not a proper fraction because the numerator is greater than the denominator, making it an improper fraction that can be simplified to "4."
d. 5/3 is not a proper fraction because the numerator is greater than the denominator, making it an improper fraction.
Therefore, the only proper fraction among the options given is c. 9/10.