Question 18 of 20: select the best answer for the question. 18. which of the following is true of red blood cells? o a. once created in bone marrow, they circulate for our lifetime o b. they live for only 120 days o c. they have multiple nuclei o d. they live for only about 20 days

Answer is B.

Explanation:

The fact that B is right eliminates A and D. C is eliminated because RBCs do not have nuclei.

bacteria could be both, harmful and to us. harmful bacteria could make us sick and probably even by getting the chances of getting a disease, but good bacteria fight it off with your immune system. there is always bacteria everywhere we go. we need to make sure to wash our hands after using the restroom, before eating, after eating, after petting an animal too. so you see, bacteria is everywhere and is harmful or . i hope this . : ) : ) : )