Which of these is a method of obtaining oil?

A. Tar sands extraction

B. Surface mining

C. Underground mining

D. Coal mining

A. Tar sands extraction

The others are used to get solids like coal or diamonds.

That's correct. Tar sands extraction is a method used specifically to obtain oil from tar sands, while surface mining, underground mining, and coal mining are used to extract solids like coal, diamonds, and other minerals.