Answer:
100 times more acidic.
Explanation:
If you look at the pH scale, pH2 is 2 "jumps" away from pH4, therefore, pH2 is 100x more acidic than pH4.
A half-life. This term can be seen in carbon dating when unstable carbon-14 isotopes turn into nitrogen-14 isotopes
7.62 decameters, 7620 centimeters
If the fossils from one shore are also on a different shore on a different continent, they probably didn't migrate from shore to shore. sorry that I didn't shorten it as much as I could.