The correct answer is B. Digitizer.
A digitizer is a device that converts analog information into digital form. This can be done by scanning an image, converting a sound recording into a digital file, or converting a video recording into a series of digital images.
A modem is a device that converts digital information into analog form and vice versa. This is necessary for sending data over telephone lines, which are designed to carry analog signals.
A mouse is a pointing device that is used to control the cursor on a computer screen. It is typically a small, handheld device with two or three buttons and a scroll wheel.
A light pen is a pointing device that is used to select items on a computer screen. It is a small, handheld device with a light sensor at one end. When the light pen is pointed at a particular location on the screen, the computer detects the light and moves the cursor to that location.
E is not the correct answer because it is not a device that changes information into digital form.