The correct option for the sentence "My sister has.... hair." is **C. long black curly**.

This option provides a clear and grammatically correct description of the hair's length, color, and texture in the appropriate order.

In English, adjectives are typically arranged in the order of quantity, opinion, size, age, shape, color, origin, material, and purpose, which is often summarized as "OSASCOMP." In this case, “long” (size), “black” (color), and “curly” (texture) follow the correct sequence.