Transmutation
a. nuclear change.
b. chemical change.
c. both a nuclear change and a chemical change.
d. neither a nuclear nor chemical change.

Answer is: nuclear change.

Transmutation is a process that involves a change in the nucleus of an atom. It can be natural or artificial.

For example: 14/7 N + 4/2 He --> 17/8 O + 1/1 H.

This example is the first artificial nuclear transmutation described by Rutherford in 1919.  

Artificial transmutation can be expressed by nuclear reaction:  

Target Nuclide + Bombardment Particle → New Nuclide + Ejected Particle.

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.

a corroding iron, if that's one of your choices