Lines are added to A to make B. Add lines to C by the same rule. Which answer figure is correct?

For every line in A a new line is drawn through the centre at right angles to it: the flat line gets an upright partner and the slanting line gets the other slant. C has one line, tilted up a little from flat, so one new line is added at right angles to it, steeply tilted the other way, and the orange dot stays: (d). (a) adds the mirror-image line, which is not at right angles, and (b) adds two lines.