Multiple Choice is the workhorse question of the new editor: one question, a list of options, exactly one of them right. True or False is the same block with the options already filled in for you.
Adding one
Type /mult, or pick Multiple Choice from the + menu. The block arrives with a Question field and two empty options.
For a true or false question, pick True or False instead. You get the same block with True and False already written in, and you still have to say which one is correct.
Writing the question and options
1. Type your question in the Question field. Rich text, inline maths and images all work here, so "Which graph shows constant acceleration?" above an image behaves the way you would expect.
2. Fill in each option. Click Add answer for more, as many as you need.
3. Click the circle to the left of the right answer. The tooltip reads Mark as correct before you click it and Correct answer afterwards.
4. Set the marks with the + and - controls in the bottom right.
Only one option can be correct. Marking a second option correct un-marks the first, because the control is a radio button rather than a checkbox. If more than one answer should count, use Select All Correct instead.
How it is marked
All or nothing. The student gets the full marks for picking the right option and zero for anything else, including leaving it blank. There is no partial credit and nothing to configure, which is exactly why these questions are worth using: the marking is instant and beyond argument.
Writing options that actually test something
The quality of a multiple choice question lives entirely in its wrong answers. An option nobody would ever pick is a wasted slot.
Build each distractor from a mistake you have genuinely seen students make. If they always forget to square the radius, make that an option.
Keep the options a similar length. A conspicuously longer option reads as the correct one whether it is or not.
Avoid "all of the above" and "none of the above". They test reading stamina rather than the subject.
Wrong answers chosen this way are worth more than the mark: the per-question breakdown then tells you which misconception a class holds, not just that they got it wrong. See The Block Detail Drawer: per-student responses.