Fill in the blanks with the most appropriate option:-

He does not work hard, ………. he will fail.

therefore

The correct option to fill in the blanks is therefore.

The word "therefore" is a conjunction that is used to introduce a conclusion that follows from something that has been said previously. In this sentence, the speaker is saying that if the person does not work hard, they will fail. The word "therefore" is the most appropriate word to use in this context, as it indicates the logical connection between the two clauses.

The other options are not as appropriate:

• Hence is also a conjunction that is used to introduce a conclusion, but it is more formal than "therefore". It is not as appropriate as "therefore", as it does not convey the same sense of directness or immediacy.
• And is a coordinating conjunction that is used to join two or more clauses that are related in meaning. It is not as appropriate as "therefore", as it does not convey the same sense of logical connection.
• If is a subordinating conjunction that is used to introduce a conditional clause. It is not as appropriate as "therefore", as it does not convey the same sense of conclusion or inevitability.