Which gland secretes chemicals that exert subtle effects on the sexual behavior and physiology of other people

The Apocine glands.

Explanation:

These glands secrete  sex  pheromones This is the chemical substances which exhibits subtle effects on the sexual behavior and physiology of other people.

They are located at the  axilla,anogenital region, at the areola and  the nipple etc,The breast is a modified apocrine gland.It contains the mammary gland which secrets the best milk.Thus it is an example of apocrine gland.Basically,pheromones  are has a significant reproductive effect on the  opposite organism concerned.It aids mating,

Their hormonal secretions is released through the plasma membrane by   budding off from the extracellular membrane,

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation:

i think the answer is a.keratin is the pigment responsible for skin color.