Fill in the blank with the correct form of tense: He ______ a fortune by…

Correct answer: is making

Explanation:

Use present continuous to show an action that is currently in progress. ‘‘Is making’’ is the present continuous form and indicates he is in the process of earning money now by writing books.

• The phrase “by writing various kinds of books” is a participle clause showing the method; it fits with an ongoing action (is making).

• Other choices are ungrammatical or use the wrong verb form: “Did making” is incorrect (should be “did make” for past simple), “Would made” is incorrect (should be “would make”), and “Will made” is incorrect (should be “will make”).

• Note: Present simple (“makes a fortune”) can also express a habitual fact, but among the given options only “is making” is grammatically correct and matches the intended ongoing meaning.