A steroid is an organic macromolecule that is biologically active with four rings arranged in a specific molecular configuration. Steroids are important components of cell membranes which alter membrane fluidity and act as signaling molecules. The two main types of steroids are corticosteroids and androgenic steroids like testosterone and estradiol.
Explanation: C and D are jokes/ complete lies. B is wrong because Darwin did observe that animals and plants adapted (evolved) to suit their environments.
