So its acquired immunity and the cells responsible are the B lymphocytes that produces antibodies against the virus. Memory is keep since first encounter of the virus by the immune system by way of the antibodies that was initially produced. The antibodies are there already, which makes it fast to act upon when expose again.
Running. D, I was going to put down, A, but D is most logical as well.
There is loads of choices so I could not really tell what the best one is. Although I wouldn't know because I'm a guy so I cant really tell what the best one is. I did look that question up and loads showed up on the right of my screen.
Sorry
If he doesn't have friends, he will not be able to have the guidance/help one should need for their life