What did protestors do at the democratic national convention in 1968? they calmly marched single file into the convention hall. they chanted and threw objects at the police outside the hall. they put up a perimeter around the convention center. they attacked a crowd of people and innocent bystanders

Correct

Further explanation:

When the Democratic National Convention met in Chicago in 1968, thousands of protesters staged demonstrations against the US involvement in the Vietnam War.  Chicago's mayor, Richard Daley, sent out 12,000 local police officers against the protesters and called in thousands more state and federal officers.  The protesters had not initially been violent, but as the tension between protesters and police continued, there were instances of protesters throwing objects.  But the police reacted with even stronger measures, using tear gas and beating protesters with clubs.

d and a is the correct anwsers

explanation: