What will come in place of ‘?’ in the following

Select the most appropriate option to replace the bold word in the given Sentence.

What are a few factors that contributes to water pollution?

Select the most appropriate synonym of the given word.

DETAIN

Select the most appropriate word for the given group of words.

a written work dealing formally and systematically with a single specialized subject.

Select the most appropriate word for the given group of words.

fear of heights 

Select the most appropriate ANTONYM of the given word.

Precarious

 Select the most appropriate synonym of the given word.

PERSIST

Select the most appropriate antonym of the given word.

PERSEVERANCE