應該是A.
or(否則).牛一定要吃穀類,否則牠們無法長胖.
Cows must eat grains,or they will not grow fat.牛必須吃穀物,否則不會長胖。(A)或(B)但是(C)當(D)雖然or (else) (conj.) 否則;要不然
23. Cows must eat grains, ____ they will..-阿摩線上測驗