What is the next element of this sequence and why?
There are more than one answers, but only one of the listed options is correct.
Consider each cross as two Cartesian axes with the same scale.
(Apparently this puzzle is really, really hard) Consider the lines that are not crosses as the graph of a function $y=f(x)$. Draw a grid (or the ticks in the axes). Any scale will be fine but some scales are more convenient than the others.
There is a progressive pattern in the sequence. That means that the answer does not have something in common with all the elements in the sequence: it really continues the sequence in some sense. Also, $[-3;3]$ is a good scale for the two axes.
Using $[-3; 3]$ as scale write the value of $f(x)$ for each diagram and for each $x \in [-3; 3]$. Now it should be clear what is the pattern