They Increase the surface area available for the absorption of nutrients
Answer:
The secondary immune response is the immune response when the same antigen , memory cells that was encountered before is remembered and the immune system make antibodies to counter it.
Explanation:
There is a difference between the primary immune response and secondary immune response.
In the primary immune response occur when the immune system encountered an antigen for the first time which lead to the generation of memory cells and and the B cells with the T cells produce antibodies.
While the secondary immune response occur when the same antigen that was encountered the first time is encountered the second time and it lead to the stimulation of memory cells to produce more and high quantities of antibodies to fight foreign substances.
Answer:
Electrons Can Donate - 0
Electrons Can Receive- 2
Valence - 2
Explanation:
The electronic configuration of oxygen is 
. Thus in the p-orbital there is deficiency of two electrons. Hence, it can receive/share electron but it cannot donate electrons. This makes oxygen as a good electron acceptor. Since there is a deficiency of two electrons in the outermost shell of oxygen, the valence of oxygen in thus -2
