Several Sections Are Included in a Research Article

Several sections are included in a research article. For example, the methods section describes the research study and what assessment quality and criteria were used. What information does the abstract or introduction section include?

A) An evidence summary from the results of several other studies
B) An outline of the number of studies retrieved and excluded and respective reasons for their inclusions or exclusions
C) A discussion about whether the results are heterogeneous with possible reasons
D) A clearly stated review question