Rina is desirous ................................ visiting Switzerland.

Correct option is C

The correct preposition with "desirous" is "of." The phrase "desirous of" is used to express a strong wish or longing for something. Therefore, "desirous of visiting Switzerland" is grammatically correct.
Information Booster:
1. "Desirous of" is a fixed expression in English.
2. "Of" indicates the object or reason for the desire.
3. Commonly used in formal English writing and speech.
4. Incorrect prepositions like "for" or "about" distort the meaning of the sentence.
Additional Information:
· (a) for: Incorrect; "desirous for" is not a valid expression.
· (b) over: Indicates control or authority, irrelevant here.
· (d) about: Suggests general information, not suitable for desire.