It has been proposed that North America is moving west at about 2 cm per year. How many kilometers would it move in 5,000 years? (Note: 2 cm is a measurement so your final answer should have significant figure rules applied.)
km
1
10
100
0.1

Icant see the pictures 

Answerionic bond imfs are stronger than covalent;

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.

It would be c. risk.