The figure below shows line $\ell$ with a regular, infinite, recurring pattern of squares, all positioned above line $\ell$. Each square has a small diagonal line segment extending from its top-outer corner. The diagonal segments alternate between pointing up-right and up-left.

How many of the following four kinds of rigid motion transformations of the plane in which this figure is drawn, other than the identity transformation, will transform this figure into itself?

• some rotation around a point of line $\ell$
• some translation in the direction parallel to line $\ell$
• the reflection across line $\ell$
• some reflection across a line perpendicular to line $\ell$