I felt terribly sorry to learn that his sister ________ after having fought against cancer for three years.

Robert gradually ____ a knowledge of aviation.

____ you understand this rule, you＇ll have no further difficulty.

Aircraft ____ large amounts of fuel.

The major ____ of air pollution in many cities is either automobiles or industrial facilities.

The first rules for air traffic control were ____ by ICAN.

Airport designers are primarily ____ the fcilities which are located on the ground.

Please don＇t let me ____ this time.

My brother-in-law only uses Colgate ____.

Just one accident can ____ millions of dollars and hundreds of lives.

The difference between an accident and a serious incident ____ the result.