Because plate movements have raised ancient sea floors above sea level,
a. there is less coral than there used to be.
b. coral reefs are only found in the deep ocean.
c. limestone that began as coral reefs can be found on the continents.
d. all remains of ancient coral reefs have been lost.

Yes he thought they should be left to chance why, because he thought that was the best thing to do

C. gemstones they are the only non metallic mineral from the list.

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature