a coordinated plan that led to the deaths of thousands of people.
Explanation:
We known this is the answer because the first "<em>completely unsuccessful in achieving their goal.</em>" is incorrect. The Twin Towers were specifically targetted, and the terrorists suceeded in taking them down. Their main goal was to invoke fear into people, and to kill thousands. Both goals were achieved.
The second answer "<em>an attack on the cities of New York and Los Angeles.</em>" is partly incorrect because while the Twin Towers were in New York, Los Angeles was not attacked in any way.
The third answer "<em>terrifying because the terrorists had bombs on planes</em>" is not true either. There were no bombs in the attack.
Thus concluding that answer D, "a coordinated plan that led to the deaths of thousands of people", is correct. (Due to the fact that it was a coordinated plan that lead to the death of 2,977 people)
