$(i)$ Why is the cell called the structural and functional unit of life?
$(ii)$ Why is the plasma membrane called a selectively permeable membrane?
$(iii)$ Name the factor which decides the movement of water across the plasma membrane.

(N/A) $(i)$ Cells are the smallest units that constitute the body of all living organisms and perform basic life processes essential for survival. Therefore,the cell is known as the structural and functional unit of life.
$(ii)$ The plasma membrane is called a selectively permeable membrane because it allows the movement of only certain selected substances into and out of the cell,while restricting the movement of others.
$(iii)$ The concentration of dissolved substances (solutes) in the water determines the movement of water across the plasma membrane,a process known as osmosis.