Form and rules
How it works
Direct questions invert an existing auxiliary/modal or use do/does/did with simple main verbs.
Subject questions do not use do-support when who/what is the subject: Who called?
Negative questions can express surprise, expectation or suggestion: Didn't you get my email?
Question tags match the statement's auxiliary and usually reverse polarity.
Choice questions present alternatives with or and normally use ordinary question word order.