One Media Report of Karpinski's Study of Facebook Use and Grades

One media report of Karpinski's study of Facebook use and grades used the following headline: "Sad but true: Using Facebook can lower your GPA." This headline is misleading because the study

A) showed that Facebook use is only a problem for first-year students.
B) merely showed an association between Facebook use and poor grades.
C) was limited to students on Facebook.
D) found a causal relationship only for humanities and social science students.