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 1.An important aspect of MCS [mobile crowdsensing] applications is that they potentially collect sensitive sensor data pertaining to individuals. 2.For example, GPS sensor readings can be utilized to infer private information about the individual, such as the routes they take during their daily commutes, home, and work locations[9]. 3.On the other hand, these GPS sensor measurements (from daily commutes) shared within a larger community can be used to obtain traffic congestion levels in a given city[4]. 4.Thus, it is important to preserve the security and privacy of an individual, but at the same time enable MCS applications. 5.It is also necessary to ensure that an individual’s sensor data is not revealed to untrustworthy third parties. 6.A problem that arises from the opt-in nature of crowdsensing applications is when malicious individuals contribute erroneous sensor data (e.g. falsified GPS readings), maintaining the integrity of sensor data collected is an important problem.Source: Ganti, R. K., Ye, F. & Lei, H. (2011). Mobile crowdsensing: Current state and future challenges. IEEE Communications Magazine, 49 (11): 32-39.