Select the most appropriate option to fill in the blank.

Writing books about how to ______ on the internet seems like a great idea.

make a fortune

The most appropriate option to fill in the blank is make a fortune.

The sentence is about the potential financial benefits of writing books about how to make money on the internet. The phrase "make a fortune" means to earn a large amount of money, which is the most appropriate word to use in this context because it describes the potential financial rewards of writing such books.

The other options are not as appropriate.

• Make a promise means to give someone your word that you will do something. This does not make sense in the context of the sentence because the speaker is not talking about making a promise.
• Make a habit means to do something regularly. This does not make sense in the context of the sentence because the speaker is not talking about making a habit of writing books about how to make money on the internet.
• Make a list means to write down a series of items. This does not make sense in the context of the sentence because the speaker is not talking about making a list of things to do.