中国大学MOOC: Mobile phone sensing is a relatively new topic that requires further academic research. Below are extracts from several academic articles discussing mobile phone sensing. Read the extracts and write down the number of the sentence or sentences that indicate the literature gaps identified by the authors that require further research. (答案写句子编号，若有多个选择，编号间空格)TEXT 11.Most examples of community sensing only become useful once they have a large number of people participating; for example, tracking the spread of disease across a city, the migration patterns of birds, congestion patterns across city roads[5], or a noise map of a city[24]. 2.These applications represent large-scale data collection, analysis, and sharing for the good of the community. 3.To achieve scale implicitly requires the cooperation of strangers who will not trust each other. 4.This increases the need for community sensing systems with strong privacy protection and low commitment levels from users. Source: Lane, N. D., Miluzzo, E., Lu, H., Peebles, D., Choudhury, T. & Campbell, A. T. (2010). A survey of mobile phone sensing. IEEE Communications Magazine, 48 (9): 40-150.