In an explanatory essay, or any essay, the introductory paragraph introduces (hence it's name) the main idea, or what you are going to explain. The body paragraphs go into extreme detail of what the introductory paragraphs mentioned.
It’s between b and d but i would choose D
<span>The power given to national government through constitution
is called Delegated Power, or Enumerated Power. These are the powers granted to
federal government in section 8, Article I of the constitution. According to
these issuing currency, commerce regulations, war declaration, armed forces maintenance
and some powers related to Post Office are the jurisdiction of national
government. </span>
