Which statement best describes cancer cells?
a. they grow as a single layer of cells.
b. they cease to reproduce after 20–50 mitotic divisions.
c. they reproduce only when needed to replace missing cells.
d. they are not regulated by contact inhibition.

Sydney drew a flow chart to illustrate the nitrogen cycle.which labels best complete the flow chart? x: producers undergo photosynthesis.y: nitrogen compounds are released into the air.x: nitrogen compounds are released into the air.y: producers undergo photosynthesis.x: free nitrogen is in the atmosphere.y: producers absorb nitrogen compounds through their roots.x: producers absorb nitrogen compounds through their roots.y: free nitrogen is in the atmosphere.

Why does meiosis produce cells with half the chromosomes? o a. most of the chromosomes are not necessary to keep an organism alive. b. a gamete needs only half the number of chromosomes because two gametes join together. o c. it makes the gametes easier to move around in the organism. o d. it is faster to produce gametes with fewer chromosomes.

Based on the topographic map of mt. st. helens, what is the contour interval of the volcano about height is 2,950 m?