@elionexis_rodri , there is no way to combine two questions together, you'd have to set it up as separate questions. Yet, I've done this before where one question was directly related to the question before it and it seemed to work ok and students seemed to get that the questions were related.
@elionexis_rodri Welcome to the Canvas Community! @kona is correct; you aren't able to give a student the option of answering a single question as either a multiple choice or via dropdowns. However (and I don't think this is what you were asking, but I wanted to offer it as an alternative), the new Quizzes LTI will allow you to create a single question prompt that is grouped with different question types. So, a student would, in response to one central prompt, answer a multiple choice question, and then a matching question, and then a fill-in-the-blank, and so forth. This is called a stimulus question, and you can learn more about it at How do I insert stimulus content in the Quizzes LTI? The Quizzes LTI is currently being beta tested by various institutions, so this tool might not yet be available in your Canvas course.
A potential work-around that may help answer the question. I wanted to include both a multiple choice question and allow students to upload a spreadsheet to show their work. I used a fill in the blank question. I showed the choices for the answers to the MC question and then used the first blank to allow students to insert their choice (i.e. A, B, C, or D). The second fill in the blank question is where I had students upload their spreadsheet link. Hope that this may help.