What does a light pen contain?

The correct answer is: B. Light sensitive elements.

A light pen is a computer input device that allows a user to select text or graphics on a computer screen by pointing at them with the pen. The pen contains a light-sensitive element that detects when it is pointed at a bright area on the screen. This information is sent to the computer, which then selects the corresponding text or graphic.

Option A is incorrect because a light pen does not contain refillable ink. Option C is incorrect because a light pen does not contain pencil lead. Option D is incorrect because a light pen does not contain blue ink.