Chalk is a soft white powdery limestone that's made with fossil shells of foraminifers. Chert is a hard dark opaque sedimentary rock which is made of silica with an amorphous fine grained texture.
In the following statements, a challenge that the agricultural faces in the coming decade would be B. Farmers in Africa must adopt new methods in order to meet their needs. The IAASTD would respond to the widespread realization about the technological achievements.
the first plants and anthropodes appear on land approximately about 470 million years ago
