Molecular biologists are interested in things like the level of gene expression (how much protein or RNA is present at any given time), which molecules are directly touching each other inside the cell, etc. ... Cell biology techniques, on the other hand, want to know what's going on inside intact cells.
( Try to see which one sounds best after reading this)
They have 46 chromosomes :)
A semipermeable membrane is a membrane that allows certain substances to pass through it. The most accurate definition is the third choice, "It is a barrier with tiny openings that let some, but not all, materials pass through." hope this helps:)