听第9段材料,回答第15~17题。 Text 9 M: Are you looking forward to your trip to Canada, Susan? W: I can't wait to see Canada, Jason, but I'm scared stiff of the journey. My husband insists on flying, but I want to sail. Planes make me nervous. M: There's nothing to be frightened of. How many planes fly across the Atlantic every day? W: I've no idea. Hundreds, I suppose. M: And how often do you hear of a crash? Once or twice a year? W: Yes, but aero-planes fly so high and fast that once is enough. M: There are more road accidents per day than air deaths per year. Air transport is really safe compared with road transport. W: I still prefer to go by sea. Ships may not travel fast but as least you can relax. I'd love a trip on a luxury liner like the Queen Elizabeth II. M: It's fine if you're a good sailor, but have you ever traveled far in a rough sea? W: No. I've only been in a boat once. I sailed down the River Thames on a sightseeing tour, but in any case I'd rather be sea-sick than dead. What is the woman afraid of when she takes her trips?