Why does the plant cell have a cell wall and a cell membrane?

When water freezes, it . contracts expands

Amniocentesis is a process in which amniotic fluid is taken from the mother's womb to identify any genetic abnormalities in the fetus. how would the discovery of the human genome contribute to this process?

During an experiment, readings for blood pressure in a persons body were found to be constant . however , when he measured by a different blood pressure cuff , the readings differed by 15 points for each reading. this difference indicates that the results are