21. By the time the convention ended how many arrests were made and how many protesters

and police were injured in 1968?

192 police were injured and there were around 10000 protesters who gathered for the demonstration.

Explanation:

In the year 1968, 28th of August protesters gathered for demonstration in Grant Park. At 3:30 p. m. the American flag was lowered by a young man, the police became angry and entered in the crowd and started beating the crowd who gathered there and the crowd started throwing rocks, part of concrete as well as food to save themselves. A police riot started and 192 Chicago police were injured and around 10000 protesters gathered.