Which of the following is not
an external force that acts on rocks in the rock cycle?

a. pressure

b. ice

c. water

d. wind

The correct answer is option A. Pressure.

Explanation:

During the rock cycle there are changes in the igneous rocks, which can become sedimentary rocks or metamorphic rocks through different processes which involve external forces to achieve it.

This cycle begins with the igneous rock, which exists since the Earth formed, since it comes from the hot magma that is inside the Earth, and when it leaves it is cooling, and once it reaches the surface it solidifies becoming an igneous rock which has many minerals.

Once this rock forms on the earth's surface, external forces appear that cause this rock to fragment or be transported: wind and water.

This fragmented rock is called sediment and through large currents of water or wind, and even ice can be transported or buried in other layers of sediment, which will allow new sedimentary rocks to form over time.

Due to the heat coming from inside the earth, the shapes of the rocks change, forming metamorphic rocks.

This cycle never stops and continues to form mountains or new rocks constantly.

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.