When performing turns to headings using the flight instruments, which of the following is a potential error of the heading indicator?

You are practicing turns to headings under the hood. After completing several 180° turns, the heading indicator shows a heading of 090° while the magnetic compass reads 100° when the wings and ball are level. The most likely cause is

When performing a standard rate turn to a heading at 120 knots TAS, the attitude indicator should show approximately what bank angle?

While executing a standard rate turn from a heading of 090° to 270°, which instrument provides the primary reference for determining when to initiate the rollout?