Where an ungrounded system is installed, non$-$current$-$carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the supply system grounded equipment in a manner that creates a low$-$impedance path for $?$ that is capable of carrying the maximum fault current likely to be imposed on it$.$

a$.$ current

b$.$ ground$-$fault current

c$.$ short circuit current

d$.$ unintentional conducting connections