How does critical mass play a role in nuclear reactions?

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Which of the following ocean acidification? are the most likely side effects of a ph less than 7.0 in the ocean b. more metal salts altering the ocean chemistry c. dissolution of the shells of marine organisms d. both a & b e. all of the above.

In a copper wire, a temperature increase is the result of which of the following