On a graph, _____________ axis shows the independent variable?

The correct answer is: x-axis

TO FIND-
Axis that shows the independent variable.
SOLUTION-
The independent variable can be referred to as the cause i.e. Its value is independent (does not change as per the other variables) of other variables. The dependent variable can be referred to as the effect. Its value depends on changes in the independent variable.
Generally, Independent variables are represented on the x-axis i.e. horizontal axis and Dependent variables are represented on the y-axis i.e. verticle axis.
Hence, x-axis shows the independent variable.
FINAL ANSWER-
Option 'a' i.e. 'x-axis' is the correct answer to the given question.