Answer: B. loess; erg
Step-by-step explanation:
Loess is a a type of soil which exhibit fine grained silt sized particles. It is formed by the accumulation of the wind blown dust. The 10% of the total land of earth is occupied by this type of soil. It consists of about 20-50 micrometer sized particles, 20% of the clay and balanced parts of sand and silts.
The erg can be define as the broad flat area of the desert which is occupied with the sandy soil. It exhibit little or no vegetation cover. The world largest erg is Sahara desert (African continent).