In this series a dot is added in a corner each time while the cross in the middle changes. Which figure is next?

The cross turns $45^{\circ }$ each step, so it alternates between an upright plus and a slanted cross, and a new dot appears in the next corner clockwise. Next: a slanted cross with dots in all four corners: (a). (b) forgets to turn the cross; (c) and (d) have only three dots.