The correct option is C Semipermeable
Respiratory membrane must be semi- permeable in nature to allow the passage of small molecules and ions. It should also support the process of diffusion. Only large molecules are transported using channels or porins. In root, the ascent of sap takes place through simple diffusion. If cell membrane was not semi permeable then it could have never happen. If it was permeable or impermeable then it is difficult for cell to survive. Thus, option C is correct.