The layer of the Earth called the mantle is often described as convecting. In this context, convection is
A.
a process that keeps the mantle stationary.
B.
a step in the formation of sedimentary rock.
C.
a continuous cycle in the Earth's interior.
D.
a process that occurs on the Earth's surface.

Amath expression is a collection of one or more terms, which are separated by the signs ( + , - , x , / ).example :   8+b8+b  or  a−3a−3in algebra, an equation is a mathematical statement with two expressions where, each expression is separated by an equal (=) sign. variables can be present on both the sides of the equality (=) sign and we use letters to denote such variables.example 1:   x=4+2x=4+2  , [here, we can observe that the variable is present only on one side of the equation].example 2:   2x+3=x+42x+3=x+4  , [here, we can observe that the variables are present on both side of the equation].

Answer they are produced by collision of tectonic plates;

Answer any resource, such as wood or solar energy, that can or will be replenished naturally in the course of time;