**urgent **
one challenge of tissue engineering is to ensure that the cells grow into the correct shape. to facilitate the growing of the cells, engineers use what?

a. biocompatible materials
b. nanotubes
c. the engineering process
d. scaffolds

hurricanes form when warm, moist air from the ocean surface quickly rises into the atmosphere and forms storm clouds and rain. when the clouds are formed, heat is released which warms the cool air in the upper regions of the atmosphere so that the cycle can continue. which two phases of the water cycle are repeated in this process?