Correct option is C
The correct option is (c) (A) is true but (R) is not true.
The assertion (A) that petroleum is called "black gold" is true. This nickname for petroleum stems from its high value and importance in the global economy, similar to the value of gold. However, the reason (R) provided, that deposits of petroleum are found in black soil, is not accurate. Petroleum deposits are not specifically associated with black soil; they are found in a variety of geological formations, often deep beneath the Earth's surface. The presence of petroleum is more related to past geological and biological processes than to the current color of the soil.