The right answer is D.
The absorption of molecules at the level of the skin is carried out by passive diffusion for the molecules of low molecular weight (lower than 400 Da), the skin being covered with a lipoprotein film rich in water by its stratum corneum, rendering it little-permeable.
This absorption may be variable according to factors related to the skin such as stratum corneum's thickness, the state of hydration, the presence of cutaneous lesions or individual variations.
External factors may also modulate percutaneous absorption such as contact time, iontophoresis or the presence of specific adjuvants.
B. I think I'm not so sure but that's my best guess.
Scientists classify rocks based on texture, composition, and how the rocks formed.] Rocks are classified by how they formed.
