Consider visual transduction in rod photoreceptors in the vertebrate retina. Which of the following steps does NOT normally amplify the signal in this pathway?

A) Activation of transducin by active rhodopsin
B) Blockage of Na⁺ influx by cation-channel closure
C) Cation-channel closure due to cGMP depletion
D) Depletion of cGMP by active cGMP phosphodiesterase
E) All of the above DO involve amplification