can u explain why highlighted is correct

Questions 10-13 ara haend 10. What is the bid-ask spread? A. $0.10 B. $0.20 C. $10.10 D. $10.20 E. None of the above 11. What is the depth at ask? A. $10.20 B. $10.10 C. 10,000 shares D. 5,000 shares E. None of the above 12. Which of the following is true after the arrival of a market buy order with quantity 18,000 shares? A. one trade will occur B. two trades will occur C. three trades will occur D. no trade will occur E. none of the above 13. which of the following is true after the arrival of a limit buy order at P=$10.30 and Q=4000 ? A. one trade occurs at P=$10.30 and Q=4,000 B. one trade occurs at P=$10.10 and Q=4,000 C. one trade occurs at P=$10.20 and Q=4,000 D. one trade occurs at P=$10.00 and Q=4,000 E. none of the above