A memory B cell is kinda of how it sounds it has a memory of what your body has fought before such as a virus and can stimulate a response quicker then the first time you encountered it.
If you lack memory B cells your body doesn't built up the same immune response when you come into contact with the virus again.
"Vaccination would prevent further disease" Incorrect, a vaccine lets you build up memory cells to combat the disease if you lack them you cannot build up a defense.
"Vaccination would not prevent further disease" Correct, a vaccine can be a dead version of a virus or parts of a virus that shows your body what to respond to quickly in the future. If you body cannot make memory b cells it wouldn't help to use a vaccine. Your body wouldn't keep a memory of it being bad.
"You would not produce antibodies" Even if your body does not remember a particular virus it does produce antibodies to combat it just not as quick or efficiantly as something it has come into contact with before and produced memory cells.
"You would over produce histamine" Incorrect, different process for that histamine.
I would say c is the answer
A solute is the part that gets dissolved in the solvent, so the solute is the sugar
Xylem and Phloem tissues are present throughout the plant. They begin at the root and then move up to the stem, branches, and leaves. The xylem tissue transports water and minerals from the roots to the leaves whereas the phloem tissue transports food from the leaves to the other parts of the plant.