Which statement about coupling and uncoupling is correct?

1. This statement confuses the tested combination-vehicle rule with an unrelated CDL topic.
2. This answer would create an unsafe coupling, braking, turning, or inspection habit.
3. This choice is not supported by the Texas CDL handbook or FMCSA combination-vehicle standards.
4. When uncoupling on a grade, chock trailer wheels in addition to setting brakes.