Which of these vehicles must stop before crossing railroad tracks?

ANSWER:

Tank trucks marked with 'hazardous material placards' is the vehicle which must be stopped before crossing the railroad tracks.

EXPLANATION:

Basically, whenever the train is about to arrive or is about to pass, then all the vehicle must stop before crossing the rail road to prevent accidents.In this case, there are tanks with hazardous materials which may cause even more accident due to which the tank truck should be stopped before crossing the rail road.

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].

Answerdistinguish between the mercalli scale and the richter scale;