Scientific questions can be asked based on what?
observations
previous research
scientific investigation
all of these

answer; ///i do believe that the correct answer is (b); ///to inform, entertain or persuade an

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.