Which option is an example of a citation?
a. paul, nikko. "dust." line drawing. the artist's page. artists unlimited, 1 february 2005. web. 5 april 2013.
b. dust storms are extremely dangerous, and people should heed warnings to find shelter when one is coming.
c. though dust storms pose a serious threat to those caught in their path, their harsh beauty is undeniable.
d. this line drawing captures both the unrelenting horror and majestic raw beauty of a dust storm.