Final answer:
William Seymour led the Azusa Street Revival, essential to the Pentecostal Movement's history, where spiritual manifestations such as speaking in tongues occurred.
Step-by-step explanation:
The statement that best describes the contribution of William Seymour to the Pentecostal Movement is that he led the meetings at the Azusa Street Revival where speaking in tongues and other spiritual manifestations occurred. This revival was a critical event in the history of Pentecostalism and is considered the birthplace of the global Pentecostal movement. Seymour's leadership in this movement was marked by inclusive and racially integrated services, which was a significant departure from the norms of the time, indirectly contributing to breaking the color barrier in the church.