copper
aluminium
iron
galvanized steel
500 ohms
1000 ohms
1500 ohms
2000 ohms
for the safety of the equipment
for the safety of the operating personnel
for the safety of the equipment and for the safety of the operating personnel
none of the above
grounding resistance should be as low as possible
grounding resistance should be as high as possible
grounding resistance should be always zero
to provide low impedance
to discharge the charging capacitance to ground
protection for operating personnel
both 1) to discharge the charging capacitance to ground and 2) protection for operating personnel