Aspirin Can Cure a Headache, but When You Pop an Aspirin

Aspirin can cure a headache, but when you pop an aspirin tablet, how does the aspirin know to go to your head rather than your big toe?

A) The body is able to "pool" medicines around areas of increased neuronal activity.
B) The aspirin doesn't "know" to go to your head rather than your big toe. Rather, it gets distributed throughout your body.
C) The blood vessels within your head are generally more accessible than those within your big toe.
D) Most commercially available aspirins are compounded with buffer agents that direct the aspirin to regions of lower pH, which includes the cerebral hemispheres.