This article covers the Legacy editor. Lessons built in the New editor work differently. To add a multiple choice question in the New editor, see Adding a Multiple Choice or True or False question. New to the difference between the two? Start with The new lesson experience.
Adding a Multiple Choice block
Open the lesson from My Library. The Legacy editor shows the lesson as a list of blocks, with the Outline down the left.
Click Add block at the bottom of the Outline.
Choose Multiple Choice. Its description in the dialog reads "Students pick from a set of options".
Fill in the block, then Click Save when you are done.
You can reorder blocks by dragging them in the Outline, and delete one from its own menu.