Which sentence contains a split infinitive?

• A. although anne was looking forward to the vacation, she was worried about leaving her job for such a long period.
• B. one of the best parts of getting ready for the trip was going to the store to buy all of the gear needed for skin diving.
• C. For your safety, we ask you kindly stay in your seats until the \"fasten your seat belts\" sign has been turned off.
• D. to be fully prepared, the campers made sure that they had checked all of the batteries in their equipment.

Answer: (C)

Split infinitives occur when an adverb or other word sits between to and the verb of an infinitive, as in to boldly go. In this sentence, the action is described with the infinitive to stay, and the word kindly appears between to and stay, creating to kindly stay. That separation is what marks a split infinitive. The other sentences either keep the infinitive together (to buy, to be) or don’t present an infinitive with to plus a verb split by another word. If we rephrase, it would naturally read as we ask you to kindly stay, which shows the intended split structure.