What is russia’s main environmental challenge today?
a. continuing the conservation policies of the soviet union
b. increasing industrial production to spare forests and farmland
c. managing its resources without disregarding the environment
d. stopping the use of nuclear and hydroelectric power sources

Russia's main environmental challenge today, in general is managing industrial production to spare forests and farmland.

East european plain and russian russkaya ravina.

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].