Dont worry those are just variables. a. and b. is the same as 1 and 2 !
Pulmonary artery carry deoxygenated blood while are there arteries carry oxygenated blood.
pulmonary vein carries oxygenated blood while the other veins carry deoxygenated blood
When red blood cells are in a higher concentrated solution, water flows out of the cells faster than it comes in. This results in crenation or shrivelling of the cell.