Which substances have Delta. Hf = 0 kJ/mol by definition? Select all that apply. O2(g) N(g) H2O(l) Br2(l) Fe(s) He(g) S6(s).

air quality

poor drinking water

and heavy polution

can lead to poor health

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.

the answer is b & c i believe : )

hurricanes form when warm, moist air from the ocean surface quickly rises into the atmosphere and forms storm clouds and rain. when the clouds are formed, heat is released which warms the cool air in the upper regions of the atmosphere so that the cycle can continue. which two phases of the water cycle are repeated in this process?