How did the boston massacre lead to the colonists declaring independence?

The Boston Massacre led to the deaths of five civilians at the hands of British redcoats on March 5, 1770, the legal aftermath of which helped spark the rebellion in some of the British American colonies, which culminated in the America Revolutionary WarExplanation:

the american rail road was the most influential and useful transportation system developed in the 1800's with steam locomotives and in the very late 1800's and early 1900's diesel electric locomotives being used to transport goods and people around the newly expanded united states!

the answer for 3 is b and the answer for 4 is d