On which axis is the independent variable usually shown in a graph?

Correct answer: Horizontal axis

The direct answer is A: the independent variable is usually shown on the horizontal axis, also called the x-axis. In an experiment, the independent variable is the factor deliberately changed by the investigator, while the dependent variable is the result measured in response. Graphing convention places the changed factor on the horizontal axis and the measured response on the vertical axis. Option A is correct because this arrangement makes the relationship easier to read. Option B is usually wrong because the vertical axis is normally used for the dependent variable, though a graph must always be checked and labelled. Option C is not the usual answer because one independent variable is normally placed on the horizontal axis, not both axes. Option D is less correct because axes should not be chosen randomly; the standard convention improves clarity. Always write the variable name and unit on each axis. Memory cue: independent is the input on x; dependent is the response on y.