Why does "4)do so" appear in the present tense, not in the past tense? Whatever one believes about the merits of completing the remaining intercity portion of the system, it is clear that 1)it gives the country an intercity transportation network that would be sorely missed had 2)it not been built. Even those who argue against 3)it 4)do so on the ground that if it had not been built, some better (nonauto) system would have been divised. --- Is it right that "1)it" indicates completing the remaining intercity portion of the system? Is it right that "2)it" indicates "the remaining intercity portion"? Is it right that "3)it" indicates the same as "1)it"? Why does "4)do so" appear in the present tense, not in the past tense? And what does "4)do so" indicate here? Please help me! Thanks!!