Hello,
Answer choice B, initiation of a cAMP second messenger system, is usually seen with polar hormones that bind to receptors on the cellular membrane which initiate these messenger cascades. Steroid hormones on the other hand have the ability to diffuse into the cell, bind to its receptor, enters the nucleus and regulate the transcription of genes (i.e. they act as transcription factors). Since aldosterone is a steroid hormone, C would be the correct choice.
I hope this helps!
-Shin