The answer is d i would say
The bodies first line of defense would be: A
Ones from that would be "tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils." - https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjAzoTz5sLT... ( Some extra info c: )
In my own words, what happens during conception. Wont let you use the bathroom right way.
the respiratory system and the circulatory system work closely together to deliver oxygen to cells and to get rid of the carbon dioxide the cells produce.
