The correct answer is A) Black.
Kerala murals are a type of Indian painting that is traditionally done on the walls of temples and other religious buildings. The paintings are usually made with natural pigments and depict scenes from Hindu mythology. The lines and outlines in Kerala murals are traditionally done in black, which helps to create a strong contrast with the other colors used in the paintings.
Option B, red, is also a common color used in Kerala murals. However, it is usually used for the background or for filling in the outlines of figures, rather than for the lines and outlines themselves.
Option C, yellow, is less commonly used in Kerala murals. It is sometimes used for the skin of figures, but it is not typically used for the lines and outlines.
Option D, green, is the least common color used in Kerala murals. It is sometimes used for plants or other natural elements, but it is not typically used for the lines and outlines.