(A p e x) Which sequence of transformations will result in an image that maps onto itself? A. Rotate 90 degrees counterclockwise about the origin, and then translate up 2 units.
B. Reflect across the x-axis, and then reflect across the y-axis.
C. Rotate 90 degrees counterclockwise about the origin, and then reflect across the x-axis.
D. Reflect across the x-axis, and then reflect again over the x-axis.

 D. Reflect across the x-axis, and then reflect again over the x-axis.

Explanation:

If we reflect over the x axis, and then reflect over that same axis again, then we arrive at the original image. Nothing has changed. This is because the two reflections effectively cancel each other out.

It's like taking one step forward, then taking one step back. You haven't moved at all.

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.

because they could drop even lower..