In OG 75, ETS explains the rule of "if x happens, y will happen". but why in OG 46, the tense is "if x happens, y happens"? is there any reason that in these two situations, the tense should be different? please see the two questions below:

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）

(E) associate with other calves, they require less medication and gain weight more quickly than

75. If the proposed expenditures for gathering information abroad are reduced even further, international news reports have been and will continue to diminish in number and quality.

(A) have been and will continue to diminish

(B) have and will continue to diminish

(C) will continue to diminish, as they already did,

(D) will continue to diminish, as they have already,（E）

(E) will continue to diminish

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.

(E) associate with other calves, they require less medication and gain weight more quickly than

75. If the proposed expenditures for gathering information abroad are reduced even further, international news reports have been and will continue to diminish in number and quality.

(E) will continue to diminish

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75題所述的句意為如果提議的資訊收集經費被刪減,國際新聞報告的質與量將會持續降低.

46題所述的句意為一但冰川與其他冰川運動與結合,他們需要較少...........並得到...........

關鍵爭點在於當 IF之意義是 "如果",則動作有時態前後關係

當 IF之意義是 "一但",則動作是同時發生,因此時態一致

例如:If Mary kisses me, I will be happy.(如果)

If I have questions,I ask Mary.(一但)

在此IF近似於Once之意,即 Once I have questions,I ask Mary.

淺見疏漏之處請指教!!