The oldest rock formation identified on Earth is found on the shoreline of Hudson Bay in Canada. This rock
formed 4.28 billion years ago. Which information does a scientist need to most accurately determine the age
of a rock
a) the percentage of each mineral that makes up the rock
b) the thickness of younger rock layers that cover the rock
c) the amount of each radioactive element present in the rock
d) the amount of weathering present on the surface of the rock

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.

who knows

explanation:

b.have there own function.

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.