Which organelle can be compared to a security guard who decides whom may enter a building and whom may not?
O cell membrane
O cytoplasm
O endoplasmic reticulum
O mitochondrion

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

b. read the phase at the intersection of any given temperature and pressure.