I think its c because solid,liquid nor plasma really fits to the description and i don't really know the last one so the best option is probably C.
Different isotopes of the same element must have a different mass number
In descriptive investigations, we still haven't formed any hypothesis yet so we seek information by asking question.
It's not repeatable because repeating the questions over and over again without any clue about what we want to seek is completely waste of time.
Hope this helps xox :)
Answer:
21 years
% of parent isotope remaining before safe
6.25%
Explanation:
It runs from 0 to 14. (A)
It is based off the -log [H+] where [H+] is the concentration of the Hydrogen ions.