What is the H.C.F. of two co-prime numbers?

Explanation: Two numbers are said to be co-prime numbers if and only if they have  as their common factor. 

The highest common factor, abbreviated HCF, is the highest (or greatest) factor of all terms in an expression or a set of terms or numbers. Hence, the H.C.F. of two co-prime numbers is 

Final Answer: Hence, the correct option is (A) .