Which sentence must be revised to eliminate the preposition at the end?

If no one answers the door, then please let yourself in.
The top steps are fine, but be careful of the slippery stairs below.
Where are Katelyn and Ella walking to?
Do you know what Naveen was talking about?

Which statement most strongly develops a positive tone? a. i was happy when i received my first paycheck for my hand work. b. winter break is approaching quickly, and i cannot wait to go shopping for gifts. c. going to the beach is one of my favorite activities; i love surfing and paddle boarding. d. a sense of accomplishment overwhelmed me as i stepped into into the stage that sunny, glorious day of graduation.