Explanation

This sentence is an indirect question, which is a polite way to ask for information.

In the indirect question, we do not invert the subject and verb as we do in direct questions.

Instead, the subject ("the cinema") comes before the verb ("is"), maintaining the normal subject-verb order of a declarative sentence.

Therefore, the correct choice is:  The cinema is

Explanation

"He is the tallest boy in the school."
Correct use of the superlative form "tallest" when comparing one person with all others in the group (the school).

Explanation

"Karachi isn't as populated as it was 10 years ago."

The sentence needs a word that indicates a comparison between the current population of Karachi and its population 10 years ago.

"As" is the correct word to express this comparison. 

Explanation

"Walk on the footpath, don't walk on the road."

We use "on" when referring to surfaces like roads and footpaths.

You walk on a footpath and walk on a road, not "in" or "at" them.

The preposition "on" correctly indicates that you are moving along the surface.

Explanation

"I wasn't feeling well, so I decided not to go to university."

"So" is used to show cause and effect in a simple, natural way. 

"So" fits the informal tone of the sentence and is the most natural choice.