What is the most important reason for citing a source when quoting it directly?

In their competition for power nations raced to

Which of these innovations led to increased production in american factories in the early 1800s? a. the use of interchangeable parts b. the construction of canals c. the invention of the mechanical reaper d. the availability of electricity

30 in 1566 the i belonged to spain. ii rebelled against spanish rule. iii was in independent country. iv was made up of both catholic and protestant provinces.