The correct answer is: a. excitement
Human sexual response cycle is a set of four phases (reactions) in human as a response to sex stimulus.
1. Excitement phase- result of physical or mental stimuli
2. The plateau phase- the period characterized by increased stimulation and increased muscle tension prior to orgasm
3. Orgasm-phase characterized by quick cycles of muscle contraction
4. The resolution phase - after orgasm characterized by the relaxation of muscles.
