I want to know your religious _____

Analyze the question: The sentence is "I want to know your religious _." The blank comes after the adjective "religious" and the possessive "your", so a noun is needed.

Explain the concept: Word-form questions test whether you can pick the right part of speech. After a possessive determiner (my, your, his) and an adjective (religious), English needs a noun. The noun here is belief (singular) or beliefs (plural).

Check each option:

• A. believe: a verb, so it cannot follow an adjective as the thing being known. ✗
• B. believing: a verb form (gerund or participle). It is not the natural noun here, and "religious believing" is awkward. ✗
• C. beliefs: the plural noun. "Your religious beliefs" is the standard phrase, since a person usually holds a set of beliefs. ✓
• D. believes: a third-person singular verb. ✗

Solution: "I want to know your religious beliefs."

Tip: When a blank follows "your/my/their + adjective", look for a noun. Eliminate the verb forms first, and you are usually left with the answer. Also note that "beliefs" is the common collocation: religious beliefs, political views, cultural practices.