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 wieght quicker than do
(B) associated with other calves, they require less medication and gain weight quicker than
(C) associate with toher 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 wieght more quickly than do
(E) associate with other calves, they require less medication and gain wight more quickly than
The correct answer is E and the explanation is: the first and last verbs in the series of verbs that describe the calves are in the present tense, so the tow in the middle should be as well: the calves exercise... associates... require... gain weight.
However the Manhattan GMAT prep for Sentence correction in Chapter 3, page 48 states that there are only 3 possibilities for the if-then clause, and that the "then" clause requires will+base verb, would/could+base verb OR would/could+have+past participle. The correct option does not follow any of these 3 structures.
How come there is a 4th option that according to the OG is correct. Can somebody please explain.
Thanks,