1.what triggers the small earthquakes that occur before a volcanic eruption a. upward movement of a magma
b. pyroclastic flow
c. cooling magma inside the crush
d. plate movements
2.what causes magma to erupt towards the earths surface
a. the density in the magma
b. dissolved gasses trapped in the magma
c. gravity of the lithosphere
d. the silica in the magma
3.this happens when temperature of lava increased
a. the viscosity increases
b. the viscosity decreases
c. can flow on short distances
d. begins to harden

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].