Which observation-and-signalling routine should an instructor teach before a learner changes lanes or turns across another road user's path?

1. Check the interior mirror, signal, and move immediately because the signal creates priority
2. Check only the exterior mirror on the changing side because it covers the blind area
3. Assess traffic with the relevant mirrors, signal in good time, make a direct blind-spot check where needed, and move only after confirming that the manoeuvre is safe
4. Make a shoulder check first, then wait several seconds without reassessing mirrors or the blind spot before moving