Detrital sedimentary rock.clastic sedimentary A+
The most densely populated European nation is the Vatican, located within Rome. It has 800 citizens with them living on a 0.17 miles squared, meaning there are 4,709 citizens per mile squared. This number might seem odd since it's much greater, but as Vatican is smaller than 1 mile, it cannot be compared without it becoming so big.
1. C 2. B 3. A 4. D In that order
'Climatic variations' and 'Human activities' can be regarded as the two main causes of desertification. removal of the natural vegetation cover（by taking too much fuel wood）, agricultural activities in the vulnerable ecosystems of arid and semi-arid areas, which are thus strained beyond their capacity.
