The correct answer is: d) excessive heating due to motor overloads and failure to start You'll find the rules for motor and branch-circuit overload protection in Part III of Art. 430 in the 2011 NEC.

Mechanical overload-protection devices, such as the EAS -Compact backlash-free, ball-detent torque-limiting clutch, can disconnect drive and driven components almost instantaneously. So-called soft ...

Motors and their associated equipment must be protected against both overload and overcurrent (short circuit or ground fault). This function is usually split, with ...