单项选择题

In the coming years, the PV sector will continue to play an important role in the global
transition from a fossil-based energy system to a renewable and sustainable one.
A、A. Explaining the significance or necessity of the research
B、B. Reviewing the existing literature relevant to the present study
C、C. Identifying a gap in the existing literature
D、D. Announcing the purpose/focus of the study
E、E. Outlining the paper structure