In December 2015, NASA's Curiosity Mars rover found the presence of ____, which will help scientists learn about the ancient wet environment.

In December 2015, NASA's Curiosity Mars rover found the presence of __

1.	In December 2015, NASA's Curiosity Mars rover found the presence of ____, which will help scientists learn about the ancient wet environment.
A.	Magnesium
B.	Cadmium
C.	Silica
D.	Calcium
Answer» D. Calcium