Why has it been difficult to decrease the gap in life expectancy between developing and developed countries? Life expectancy has increased at similar rates.
The gap between health care access and quality has increased.
Infant mortality rates have remained high in developing countries.
Poverty has limited life expectancy in developing countries.
Life expectancy has increased faster in developed countries.

Europeans are more concentrated in urban areas.

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].

Answerseafloor spreading;

The answer would be  b. hope this !