The correct option is D 5−1−4−2−3−6
The function of a kWh meter is to record the electrical energy consumed in kWh. Main fuse is a safety device that is connected in the live wire and it gets burnt in case of high current, thereby saving the appliances. MCB or ELCB is an additional safety device that gets automatically turned OFF, in case of overloading or any means of faulty condition. The switchboard is a device that directs electricity from one or more sources of supply to several appliances in usage like fans, TV, etc.
Therefore, the correct order is 5−1−4−2−3−6.