What does it mean for a membrane to be selectively permeable?

only certain molecules are allowed to pass through.

the membrane is rigid and only allows water to pass through.

all types of molecules are able to pass into the cell.

the membrane is rigid and nothing can enter or leave the cell.

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point

Iwanna go do something with my ideas? ?

The arrows in the illustration point to