3 disturbing questions

[Mesmerized]

Dear users,

I've got a question. Actually, three questions.

1. Which is the correct form?

a) You're saying you can't do it.
b) You say you can't do it.

I often hear the present simple here but the continuous form seems more appropriate since the act of speaking is happening at this very moment.

2. What's the difference between:

a) He doesn't tell us exactly what we should be doing.
b) He doesn't tell us what we should do.

3. The last question concerns it/that/this i.e. I never know which one to choose... What's more I can't actually find any reliable rules for that. And even if I do, then in the actual speech they seem to blur... For instance:

a) You can do it.
b) You can do that.
c) You can do this.

Thanks, hope it's not too much...

[Beeesneees]

1 - both are acceptable.

2. - 'exactly' - tell us in detail. the other is tell us in a more general sense.

3. All are often interchangeable. There is no hard and fast rule.
_________________
Cheers m' dears!

[Mesmerized]

I made a mistake while writing the posting... I meant:

a) He doesn't tell us exactly what we should be doing.
b) He doesn't tell us exactly what we should do.

[Beeesneees]

Both are used interchangeably.
In my opinion (and that's all it is)
What we should be doing - focuses on the 'doing' - the action.
What we should do - focuses on 'us'. - our part in it.
_________________
Cheers m' dears!