Without the greenhouse effect, earth would be
a. too cold to support our current ecosystem
b. too warm to support our current ecosystem
c. too wet to support our current ecosystem
d. barren of all life

a. too cold to support our current ecosystem

Greenhouse effects help keep the earth warm.The earth has a natural greenhouse effect. It has been there since the beginning and has sustained life ever since.Naturally occurring greenhouse gases such as carbon dioxide and methane allow solar radiation to reach the earth's surface, while trapping radiation from the earth on its way back out to space.The trapped energy warms the earth's surface , making it about 35 degrees Celsius warmer than if we didn't have the greenhouse  gases in the atmosphere. There would be no life on earth without the warmth provided by this natural greenhouse effect.

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].

Ibelieve the answer is c. map projections.hope my answer has you : )