—How far is it from Beijing to Haikou?
—It's a______ flight from Beijing to Haikou.
A. 3-hour-long B. 3 hours long C. 3 hours' long
—How far is it from Beijing to Haikou?
—It's a______ flight from Beijing to Haikou.
A. 3-hour-long B. 3 hours long C. 3 hours' long