A. is not equivalent while b and c are equivalent.
a. isn't equivalent because 3/4 with the denominator of 12 is 9/12. Therefore, 9/12 isn't equal to 10/12.
b. is equivalent because -5/10 is shortened to -1/2. At the same time, -4/8 is also shortened to -1/2. Therefore, it is equivalent.
c. is equivalent as well because 10/8 into a mixed fractions is 1 2/8. Which simplified is equal to 1 1/4. Which, is equivalent to 1 1/4/
Hope this helped.