Chemotaxis is movement of a motile cell or organism, or part of one, in a direction corresponding to a gradient of increasing or decreasing concentration of a particular substance.
Answer:
3.9 billion years
Explanation:
The half-life of potassium-40 is the time it takes for half of it to decay.
After one half-life, half of the original amount will remain.
After a second half-life, half of that amount will remain, and so on.
We can construct a table as follows:

We see that the mass will drop to 10 g after three half-lives.
1 half-life = 1.3 billion years
3 half-lives = 3.9 billion years
Kurt: " I think genes are found on DNA." Because genes are actually coded by the base sequence of a DNA strand.
C. spinal nerves
it is the answer to your question.
It doesn't show the choices but, Biostimulation<span> involves the modification of the environment to stimulate existing bacteria capable of bioremediation. </span>