Answer:
3
Explanation:
The half-life of a radioactive isotope is the time it takes for the mass of the sample to halve.
This can be rewritten as follows:

where
m(t) is the mass of the sample at time t
m0 is the original mass of the sample
n is the number of half-lives that passed
We see that if we take n=3, the amount of original sample left is

So 3 (3 half-lives) is the correct answer.
Properties and characteristics of the organism(mostly eukaryotes )determin e the kingdom
Answer:
<em>A hypothesis</em> is a limited explanation of a phenomenon; a scientific theory is an in-depth explanation of the observed phenomenon.
<em> A law</em> is a statement about an observed phenomenon or a unifying concept, according to Kennesaw State University. ... However, Newton's law doesn't explain what gravity is, or how it works.
Answer:
light doesn't need a medium through which to travel because the speed of light is experimentally constant