Together, three natural elements make up 99 of the Earth's biomass. Which of the following is not one of those three elements?
A) oxygen (O)
B) hydrogen (H)
C) nitrogen (N)
D) carbon (C)
Question 2
In the soil, which of the separates are associated with significant chemical activity?
A) Sand
B) Silt
C) Clay
D) Aluminum
E) Radium