You Are Reading a Paper in the Journal Vaccine That

You are reading a paper in the journal Vaccine that analyzed and combined the results from five observational studies involving over 1 million children and another five studies that compared children with autism to children without autism (a total of nearly 10,000 children) .The paper you are reading is best recognized as a

A) secondary literature source.
B) meta-analysis and primary literature source.
C) cohort study.
D) case-control study.