Which of the following measurement defines a measurement in inches?

px
in
em
pt

The correct answer is B. in.

A pixel (px) is a unit of measurement used in computer graphics to represent a single point on a display device. It is the smallest addressable element in an all points addressable display device.

An inch (in) is a unit of length in the imperial and US customary systems of measurement. It is currently defined as 1/12 of a foot, or 2.54 centimeters.

An em is a unit of length used in typography. It is defined as the width of the capital M in the current font.

A point (pt) is a unit of length used in typography. It is defined as 1/72 of an inch.

In the context of the question, the only unit of measurement that defines a measurement in inches is in.