When inspecting the exhaust system for defects, which of the following should be fixed?

Exhaust system defects can be extremely serious because they may make it possible for poisonous fumes to enter into the cab or sleeper berth. Issues to check for in a pre-trip inspection include loose, broken, or missing exhaust pipes, mufflers, tailpipes, vertical stacks, mounting brackets, clamps, bolts, or nuts; exhaust system parts that are rubbing against fuel system parts, tires, or other moving parts of the vehicle; and exhaust system parts that are leaking.
DMV Writen Test