Which of the following is not a common type of fiber-optic cable?
∙ A. single-mode step-index
∙ B. multimode graded-index
∙ C. single-mode graded-index
∙ D. multimode step-index
∙ A. single-mode step-index
∙ B. multimode graded-index
∙ C. single-mode graded-index
∙ D. multimode step-index