Question

al - qaedas main targets on september 11, 2001, were
boston, pennsylvania, and new york city.
pennsylvania and washington, dc.
new york city and washington, dc.
boston, new york city, and washington, dc.

Explanation:

On September 11, 2001, Al-Qaeda's hijacked planes targeted the World Trade Center in New York City, the Pentagon in Washington, DC, and a fourth plane crashed in Pennsylvania (a target likely in DC that was foiled). The main intended targets were New York City and Washington, DC, with Pennsylvania being a crash site of a diverted plane, not an intended target location.

Answer:

New York City and Washington, DC.