1) density-dependent inhibition is explained by which of the following? a) as cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce growth factors. 1) b) as cells become more numerous, the cell surface proteins of adjacent cells bind to each other and send signals that inhibit cell division. c) as cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor. d) as cells become more numerous, the level of waste products increases, eventually slowing down metabolism.