The word that can be substituted for the phrase “Ready to believe anything” is “credulous.”

• Credulous: Describes someone who is too ready to believe things and is easily fooled or deceived.

Here's an explanation of the options:

Credible: Means believable or trustworthy. This does not fit the context of being ready to believe anything, as it implies trustworthiness rather than gullibility.

Incredible: Means difficult to believe or extraordinary. This is not suitable because it refers to something that is hard to believe, not someone who is easily deceived.

Credulous: Describes someone who is willing to believe too readily, often without proper evidence. This fits the context of being "ready to believe anything."

Incredulous: Means skeptical or disbelieving. This is the opposite of being ready to believe anything, as it describes someone who is doubtful or unwilling to believe.

Therefore, "credulous" is the most accurate substitution for the phrase “Ready to believe anything” because it conveys the idea of someone who is easily deceived due to their readiness to believe in things.