From the diagram, when the temperatures of reactants are raised from 20°c to 30°c:
a. the average kinetic energy doubles.
b. the number of molecules doubles.
c. the total number of collisions doubles.
d. the number of molecules having er or greater doubles.

D. The number of molecules having Er or greater doubles.

Explanation: As the temperature increases from 20°C to 30°C, the number of molecules with maximum energy decreases, but the number of effective collisions which result into the formation of product doubles.

This is due to doubling of molecules which  possess energy equal to or greater than which means now double number of molecules will be able to cross the energy barrier and hence the formation of product increases and hence the rate increases to double.

coral.

explanation:

coral. many marine organisms that produce calcium carbonate shells or skeletons are negatively impacted by increasing co2 levels and decreasing ph in seawater.

specific gravity is the density of a substance divided by the density of water. since (at standard temperature and pressure) water has a density of 1 gram/cm3, and since all of the units cancel, specific gravity is usually very close to the same value as density

so "c" is the answer

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