Question: Which year did Alvin Cheng organize the rally with his schoolmates in support of the hong kong umbrella movement?
Sentence (from "Umbrella Movement"): Its name arose from the use of umbrellas as a tool for passive resistance to the Hong Kong Police during the occupation which was sparked by the decision of the Standing Committee of the National People's Congress (NPCSC) of 31 August of that year which prescribed a selective pre-screening of candidates for election of the region's leader.
Relevant evidence: No