Match the time period in column 1 with the correct population description in column 2. A:20th century
B: Black Plague pandemic
C: 1950 to 2000
D: Industrial Revolution
1:Population increased by at least 38 millions each year
2: When human populations began a rapid increase
3: The last drop in human population rates
4: The population doubled twice

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;

The answer to the first one is barometer.