Nowadays civil engineering does not only deal with designing fancy buildings, but also _____________ and __________everyday infrastructures

Existing infrastructures can be improved by retrofitting, which involves simply modifying the equipment that is already in service. (Para.6)[Analysis]“Which involves simply modifying the equipment that is already in service” is a non-restrictive attributive clause 1 the gerund, specifying the contents of “retrofitting”.[Translation] 2 ，这只需要对现有运行的设备做些改进。