Which statement about skids and jackknife 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. Locked tractor drive wheels can let the trailer push the tractor into a jackknife.