Function of vitamin A in the human body

Hey me with this one❤❤❤❤ every organism needs food. does a cell also need it? explain very briefly.

How does a gymnosperm prevent itself from pollinating the same tree

Which of the following types of stars is most likely to end up as a supernova? in graph a, the curve peaks at 800 nm, in the red section of the visible light spectrum. in graph b, the curve peaks at 550 nm, in the green section of the visible light spectrum. in graph c, the curve peaks at 450 nm, in the blue section of the visible light spectrum. in graph d, the curve peaks at 300 nm, in the violet section of the visible light spectrum. a b c d