Hi,

Can anyone please explain the usage/difference of the following .

1) its , it's

2) <someone> would have done,
<someone> could have done.

3) ..... so that they could do it,
......so that they could do so.

I am very weak in verbal section. However, I am writing my own understanding on your questions.
1) its , it's
its> of it
it's> it is

3) do it> is always wrong in GMAT [according to MGMAT SC review]

chaitanyareddy wrote:Hi,

Can anyone please explain the usage/difference of the following .

1) its , it's

2) <someone> would have done,
<someone> could have done.

3) ..... so that they could do it,
......so that they could do so.

1. "Its" is possessive (belonging to it), "It's" is the contraction of "it is". People confuse the two because other possessives have the apostrophe (like "George's") . . . but so do contractions (like "can't"). The difference between "Every dog knows its master" and "Every dog knows it's master" is significant.

2. "Would" is both the past tense of "will" and a modal verb with many uses. "Could" is the past tense of "can" and a modal verb expressing possibility.

3. "It" needs to replace a noun, "so" refers back to an action.

"I wanted them to do a job, and I left them alone so that they could do it."
"I wanted them to paint the house, and I left them alone so that they could do so."