Which of the following best describes the differnce between a source and a mouth? a) a source is where a river or stream originates, and a mouth is where it empites into another body of water? . b) a source is where a river or stream empties into another body of water, and a mouth is where it originates.? c) a source is partially surrounded by land, and a mouth is completely surrounded by land.? d) a source is completely surrounded by land, and a mouth is partially surrounded by land.

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].