A sand dune is considered active when
A) it is being moved by wind.
B) it is being colonized by new plants.
C) it has been formed by volcanic activity.
D) it is being dissolved into the sea.
Question 2
The largest typical size for grains of sand that can be commonly moved by wind is
A) 5 micrometers.
B) 0.5 millimeter.
C) 1.0 millimeter.
D) 1.0 centimeter.
