Typing in red a. is interpreted as yelling or anger b. is a good way to catch your readers attention c. to emphasize important points d. is essential when writing emails

I would say it is C. emphasizing certain points, because in a way, catching the readers attention is partially true but not the correct answer. Because by emphasizing certain points, you ARE already catching the readers attention. So the most truthful answer is C.

c.helps to emphasize important points

By typing in red you can emphasize important things in your writtings, it´s important to be carefull because it can also be read as an agressive color so be sure what you´re typing in red won´t be missunderstood.

i think the life is invaluable.

you can also say immeasurable.

i think the answer would mist likely be an adjective clause, because unhappy is an adjective.