Q: In which section of the paper should the research question be included?

Typically, manuscripts are divided into the Introduction, Methods, Results, and Discussion sections. This is referred to as the IMRAD structure. The research question, the objective or hypothesis of the study, helps to set up context for what you have researched and why you chose to study this particular topic. Therefore, it is included in the Introduction of the manuscript. When you write the Introduction, you should first set the background and give a review of the existing literature. This is usually followed by the research question. Thus, typically, the research question is included at the end of the Introduction section.

Related reading:

• What is the best way of stating the background of a study? 
• Tips for writing the perfect IMRAD manuscript