A.I. Explanation:

Option 1: "The subjects the artists painted are varied."

Explanation: The text describes various animals depicted in the Lascaux Grotto paintings, such as bulls, wild horses, reindeer, bison, and mammoths. This variety supports the idea that the subjects are indeed varied, aligning with the main idea of the text that highlights the diversity of the prehistoric paintings.

Option 2: "Artists painted pictures on both walls and bones."

Explanation: The text specifically mentions that the paintings are found on rock surfaces, not on bones. Therefore, this option is incorrect as it introduces information that is not present in the text.

Option 3: "Artists ground them into a fine powder to make paint."

Explanation: While the text states that colors were derived from ocher and other iron oxides ground into a fine powder, it does not imply that bones were ground for this purpose. This option misrepresents the source of the paint, making it incorrect.

Option 4: "Artists developed special techniques for painting the walls."

Explanation: The text discusses various methods of applying color, such as brushing, smearing, and spraying, indicating that artists indeed developed special techniques for painting the walls. This aligns with the main idea of the text regarding the artistic methods used.