A, AN, THE or zero article 1

Question 1

We use THE:
The unique things, ex: The sky.
To general geographical areas. The land.

Some of these nouns can be zero article:
Sun, land, sea, climate.

If we can say a particular instance of these nouns, we can use A/AN:
A bright blue sky.

Answer 1

The world, the atmosphere, the sun, the ground, the climate, the horizon, the human race, the environment, the travel industry, the internet.

The beach, the land.

She dreamt of a future where she could spend more time painting.

Question 2

We can use THE in generalizations and A/AN in particularities.

We can use plurals instead of THE.

If we use THE with plurals or uncountable, it means the particular of the thing:
The computers have arrived.

To define something or say what is typical of a thing, we use A/AN.
A corkscrew is a gadget to get a cork out of bottles.

Answer 2

The computer has revolutionized publishing.
A computer is an important tool.
Computers are an important tool.

The music was wonderful. I could listen to it all night long.

A garden is there to give you pleasure, not to be a constant worry.

Question 3

With uncountable, don’t use article. But, if they are used in a form of countably, we can use A/AN.

Answer 3

I don’t drink coffee.
Would you like a coffee? (a cup of coffee).

I shook with fear.
He has a fear of heights.