Final answer:
The correct sequence in Masters and Johnson's sexual response cycle is excitement, plateau, orgsm, resolution, with specific physiological changes occurring in each phase (option a).
Step-by-step explanation:
The correct sequence of events in Masters and Johnson's sexual response cycle is: excitement, plateau, orgsm, resolution. During the excitement phase, there is tumescence with marked changes in the genital areas such as tumescence or sensitive female organ enlargement and birth canal lubrication. The plateau phase is characterized by the continuation of the physical changes that started during excitement but at a more intensified level.
At the orgsm phase, there are rhythmic contractions in the pelvis and reproductive organs, with ejaculation occurring in males. Lastly, during the resolution phase, the body returns to its pre-arousal state with a decrease in blood pressure and muscular relaxation. This phase includes the refractory period for males where they are unable to achieve orgsm again for a certain period.
Hence, the answer is option a.