[E]OG-46，请指点！

excellent

46. A study commissioned by the Department of Agriculture showed that if calves exercise and associated with other calves, they will require less medication and gain weight quicker than do those raised in confinement.
A.associated with other calves, they will require less medication and gain weight quicker than do
B.associated with other calves, they require less medication and gain weight quicker than
C.associate with other calves, they required less medication and will gain weight quicker than do
D.associate with other calves, they have required less medication and will gain weight more quickly than do
E.associate with other calves, they require less medication and gain weight more quickly than

答案是E。我想问的是，x will happen if y happens不是正确用法吗？那么E中require应改为will require才对呀？为什么？

xiaoyue45084508

表示一种客观事实用一般现在时态