Read this passage:
two french brothers invented the hot air balloon. they made the balloon out of paper and filled it with smoke. the smoke warmed the air inside the balloon. this made it lighter than the cool air outside the balloon. it was light enough to rise into the sky.
which sentence best summarizes the passage?
a. a hot air balloon contains smoke, which warms the air in it and makes it lighter than the air surrounding it.
b. two french brothers built the first hot air balloon from paper, warming the air inside with smoke so it would rise.
c. here is the rest smoke warms the air in a hot air balloon so the balloon is able to rise into the sky.
d. the first hot air balloon was invented by two french brothers and was made out of paper.