单项选择题
How many tons does the cargo 737 carry? （）
A. 100 tons B. Not clear C. more than 100 tons D. I don’t know
单项选择题 Where is the most air freight shipped in the passenger aircraft?（）
单项选择题 How much is the percent of air transportation in all modes? （）
单项选择题 what kind of products do the air carriers deliver? （）
