The half-reactions involved in the lactate dehydrogenase (LDH) reaction and their standard reduction potentials are: Pyruvate + 2H+ + 2e → lactate E' = -0.185 V NAD+ + 2H+ + 2e → NADH+H+ E' = -0.315 V Assume that the temperature is 25°C.
Write the equation for the coupled reaction for the reduction of pyruvate.

answer; i believe that the correct answer is (a); a large rock being weathered by wind and rain;

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3

it is b that is the answer.