Given the integers a,b,c,and d where b and d ≠ 0,which shows the rules in subtracting fractions with

Given the integers a,b,c,and d where b and d ≠ 0,which shows the rules in subtracting fractions with

"a. a/b - c/d = (a-c)/2b
b. a/b - c/d = (ad - bc)/ bd
c. a/b - c/d = (ab - bc)/b
d. a/b - c/d = (ac - bd)/bd​"