How do meteorologists use isotherms and isobars?

a. to identity high- and low-pressure systems
b. to identify areas of high and low water vapor
c. to differentiate between seasons
d. to provide estimates for the amount of direct sunlight received

A. To identity high- and low-pressure systems

Explanation:

Isobars are similar to the level lines on a topographic map, showing areas of similar pressure, they are also drawn in circles to represent the areas of similar air pressure over a geographical map.

Isotherms are usually displayed in color showing areas over a map that have the same temperature or are covered by a similar temperature system (heat or cold front for example).

Both are used in electronic media mostly (although in print in newspapers too), over a geographic map to position the systems.