I really need help on these questions

What is the significance of the protein-lined pits? a. protein attracts other proteins needed for atp synthesis within the cell. b. protein-lined pits are able to transport one molecule at a time down the concentration gradient within the cell. c. the polarity of proteins allows other polar molecules to attach and be transported in the cell by transport channels. d. receptors within the pits allow ligands to fuse and be transported into the cell by endocytosis.

Which tool could you see a plant cell? a. a filter b. a microscope c. a microwave d. an electromagnet

Ruby is conducting an investigation. an advantage of her design is that she can use a large range of variables, with that she can not be sure that one variable is the cause of another. what kind of investigation is ruby most likely conducting?