Which of the following is a conductor of electricity?

Which of the following is involved in the working of a torch bulb? 

The cells/batteries which can be recharged are usually those used in:

A. Electric clocks      B. Mobile phones       C. Cameras        D. T.V. remotes

The coloured plastic covering on an electric wire makes the electric wire:

A torch bulb which normally works on $4.5$ volts electricity is connected to domestic electricity supply of $220$ volts. Which of the following will happen to this torch bulb?

The positive terminal of an electric cell was connected to a torch bulb fitted in a bulb holder. The other end of bulb holder was connected to a crocodile clip. The negative terminal of cell was connected to another crocodile clip by a wire. When a material X was held between the two free ends of the crocodile clips, the bulb did not glow but when another material Y was held between the two free ends of the crocodile clips, the bulb started glowing. 

What is the general name of the materials like (i) X, and (ii) Y?

The positive terminal of an electric cell was connected to a torch bulb fitted in a bulb holder. The other end of bulb holder was connected to a crocodile clip. The negative terminal of cell was connected to another crocodile clip by a wire. When a material X was held between the two free ends of the crocodile clips, the bulb did not glow but when another material Y was held between the two free ends of the crocodile clips, the bulb started glowing. 

Name one material each which could behave like (i) X, and (ii) Y.