In the event of a major scandal, which kind of committee would be convened to conduct a special investigation?

That depends on the details. With the whole Trump and Russia saga, congress could elect to form a commission like the 9/11 Commission or they could form a select committee like the House Select Committee on Benghazi. The idea is to have an investigation that claims more authority that a standard congressional committee. So, the correct answer is A JOINT COMMITTEE. 

Ibelieve the answer to be e