Which of the following is a marker to the surrounding individuals?

Explanation

A pheromone is a chemical factor secreted or excreted by the body into the surroundings in very small doses. It acts as an external signal to other individuals of the same species. The body of a sexually active person sends out an increased amount of pheromones and this 'sex perfume' makes him or her attractive to the opposite sex. Thus, the more sex a person has, the more sex he or she is likely to be offered.