Air mass, letter a is the correct one
LEDC means that a country is a developing country (as opposed to a developed country). This distinction is connected to the Brandt line which divides the world into developed and developing country, and India is south of this line (=LEDC, less developed country). Some reasons for this is malnutrition, high child mortality and short life expectancy.
Sand sheets and dunes cover approximately 25 percent of the Sahara's surface.
