如何在这样的数组中取消70到80之间的一系列键？
[63] => Computer Science and Informatics
[64] => Dentistry
[65] => Development Studies
[66] => Drama, Dance and Performing Arts
[67] => Earth Systems and Environmental Sciences
[68] => Economics and Econometrics
[69] => Education
[70] => Electrical and Electronic Engineering
[71] => English Language and Literature
[72] => Epidemiology and Public Health
[73] => European Studies
[74] => French
[75] => General Engineering and Mineral & Mining Engineering
[76] => Geography and Environmental Studies
[77] => Geography and …