Our understanding of science, technology, and markets has improved since the Clean Air Act was passed in 1970.
Since the Clean Air Act was passed, we have understood science, technology and markets better.
Since the Clean Air Act was passed, we have not understood science, technology and markets.
The people are having a barbecue.
A person filling a balloon.
The Shakas overrun the Greeks in the first century B.C.
A baby is asleep in a crib on the subway.
A group of people are in a horse buggy.
A man jumps into the water.