ENGLISH

The following question refers to APA Style.
Which of the following examples if a correctly formatted short quotation?
a.   Social networking has increased immensely among teenagers whereby "about 80% of teenagers frequent social networking sites on a daily basis (Shark, 2009, p. 83)."
b.   Social networking has increased immensely among teenagers whereby "About 80% of teenagers frequent social networking sites on a daily basis (Shark, 2009, p. 83)".
c.   Social networking has increased immensely among teenagers whereby "about 80% of teenagers frequent social networking sites on a daily basis." (Shark, 2009, p. 83).
d.   Social networking has increased immensely among teenagers whereby "about 80% of teenagers frequent social networking sites on a daily basis" (Shark, 2009, p. 83).