What does it mean to impregnate xylem a cell wall?

In the example of adrenaline signaling, which steps represent an amplification of the signal? question 1 choiceschoice a., activated receptor activates g proteins, g protein binding by gtp, cyclic amp activation of protein kinase achoice b., activated receptor activates g proteins, activated adenylyl cyclase produces camp, active protein kinase a phosphorylates target proteinschoice c., receptor signal binding, activated receptor activates g proteins, activated adenylyl cyclase producing campchoice d., receptor signal binding, activated adenylyl cyclase producing camp, active protein kinase a phosphorylating target proteins