Does diffusion transport direction down or against concentration gradient

Explain the popular saying "we are made of stardust. how are we made of stardust? use scientific vocab.

Which of the following statements is true about taste bud preferences? a. taste buds respond exclusively to a certain taste sensation, like saltiness. b. taste buds have the ability to respond to all of the taste sensations. c. taste buds do not differentiate between bitter and salty sensations. d. taste buds have the capability to detect three taste sensations.

Why are radio observatories located in valleys far away from urban centers? a. to shield them from electromagnetic interference b. to avoid sound pollution c. to avoid disturbing people living in the city d. to shield them from water vapor