How did Bob Dylan change rock forever?

Select one:
a. By paving the way for the creation of folk rock when he allowed the Byrds to record "Mr. Tamborine Man", which went to #1 on the charts
b. By intoducing the Beatles to marijuana
c. By combining original, thought provoking and poetic lyrics with an electric rhythm and blues sensibility
d. By staying within the parameters of acoustic folk music