A. It is true because their does not exist any number other than 1 which is a factor of both the prime numbers. Hence, 1 is also the HCF.

B. It is true as Numbers which do not have any common factor other than 1 are co-prime. Hence, for them 1 is also the HCF

C. It’s true since for two consecutive even numbers, only 2 is the HCF.

D. It’s false because an odd number can never have 2 as its factor and hence the HCF can never be even.