a.

'Upright' is basically vertical (its main axis runs up and down), but need not be mathematically so, and often is used in a metaphorical sense, as in 'Matt Dillon was an upright marshal'.

'Vertical' is (relatively) mathematically aligned with its long axis parallel to the direction of earth's gravity, or at 90 degrees to the horizon (to the 'horizontal', with which the word is often contrasted).

'Perpendicular' often refers to being at right angles (90 degrees) to the horizon, but also means at 90 degrees to any other line or surface. 'perpendicular' usually requires reference to this other line or plane-- 'my fence runs perpendicular to my driveway'

As you can see in the dictionary, there are other uses where the terms differ.


b. Either exclamation is OK. The first form suggests that you told him/her more than once previously, where the latter suggests that you said it only once before.


c. 'I'm done' = I'm finished, I'm exhausted.