درس چهارم کتاب 504 ****به همراه فایل صوتی****
درس چهارم کتاب 504 ****به همراه فایل صوتی****. a- Scientists have devised methods fer trapping vapor in bottles so they can study its makeup. b- He has gathered data on the amount of vapor rising from the swamp. c- A vapor trail is the visible stream of moisture left by the engines of a jet flying at high altitudes.