D) The AV valves are supported by chordae tendineae so that they do not blow back up into the atria during ventricular contraction.
DNA replication<span> is </span>semi-conservative<span> because each helix that is created contains one strand from the helix from which it was copied. </span>
Because it determines if it is isolated or not. This means if other substances can enter or not. This usually relies on the membrane with it´s pores. The pores help the membrane be selectively permeable in what it lets in and out.
Answer:
Its D, The cell membrane(also known a the plasma membrane) has a job in which it has to allow passage in and out of the cell. Therefore it can prevent harmful substances from entering the cell. Think of it as security, either allowing you access or denying you depending on if you're a threat
