Fill in the blank with the most appropriate ANTONYM of the underlined word.
Gentlemen always go for a lawful approach, but rouges choose ______ ways to solve problems.

The correct answer is illicit.

Explanation:

The word lawful means conforming to, permitted by, or recognized by law or rules (i.e., legal).

An antonym is a word opposite in meaning to another word. Therefore, we need a word that means not permitted by law or illegal.

Let's look at the given options:

1. Sophisticated: Having, revealing, or involving a great deal of worldly experience and knowledge of fashion and culture (Not an antonym of lawful).

2. Illicit: Forbidden by law, rules, or custom; illegal or unlawful. This is the exact opposite (antonym) of lawful.

3. Legitimate: Conforming to the law or to rules (Synonym of lawful, not an antonym).

4. Legal: Appointed or required by law (Synonym of lawful, not an antonym).

Hence, the sentence completed with the correct antonym is: "Gentlemen always go for a lawful approach, but rogues choose illicit ways to solve problems."