Directions: In the following question, four statements are provided between an opening statement 1 and a closing statement 6. The four statements are jumbled up and form a coherent paragraph when properly arranged. Select the alternative representing the proper & logical sequencing of these six taken together.

(1) There are many types of photo electric cells, and they are used for many things. (A) This happens because our body blocks a beam of light and a photoelectric cell makes the door open. (B) One of the most familiar ones is when a door seems to open by itself when we approach it, as we often see at airports. (C) When light strikes certain chemical substances such as selenium and silicon, its energy causes a push on the electrons in the substances. (D) Light is a form of energy. (6) If two different substances touch one another, some electrons may leave one and enter another.