What characteristic of the semipermeable membrane determines which substances can pass through?

Johnny rode his bike 4 blicks down the street to his friend's house once he got to his friend house and realized he could not cone out to play he turned aroubd and went back home.what is 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

Which of these substances does not protect against invaders in the nonspecific immune response? a. saliva b. mucus c. tears d. urine

Which step is not included in the step approach to calculating the greatest common divisor?