A freight train weighing 12,000 tons is traveling 65km/hr. How far will it travel in 18 hours?

What does it mean for a cell membrane to be selectively permable

Why is excretion necessary to maintain homeostasis?

Photosynthesis uses co2 and cellular respiration produces co2. we call the point when the two processes are in balance--when there is no net production of co2--the compensation point. how might you limit one of the processes in order to achieve a compensation point?