Which statement is true about oxidation-reduction reactions? a. every oxidation must be accompanied by a reduction. b. there are four commonly accessed oxidation states of carbon. c. dehydrogenases typically remove two electrons and two hydrides. d. they usually proceed through homolytic cleavage. e. during oxidation a compound gains electrons.

Every oxidation must be accompanied by a reduction.

Explanation:

Oxidation and reduction are complementary processes. There can be no oxidation without reduction and vice versa. It is actually a given an take affair. A specie looses electrons which must be gained by another specie to complete the process. This explains why the selected option is the correct one.

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

6.4 cm (max) - 25 cm (min)