III. Choose the best words to complete the following sentences(20%). breakthrough, upgrade, compatible, analysis, monorail, integrated, principle, interlocking, subsystem, maintenance ( 1 ) During the recent years, train technology has experienced great . ( 2 ) Vehicles must run according to the in order to keep safety. ( 3 ) New technologies must pass tests before putting into use. ( 4 ) Windows software is with its lower levels. ( 5 ) is another technology in the train operation. ( 6 ) The Chinese Train Control System (CTCS) has two : ground subsystem and onboard subsystem. ( 7 ) Software should be often to catch up with the passengers’ demands. ( 8 ) After any accident, the experts need to make some to avoid the similar affairs happen again. ( 9 ) i s a railway system in which trains travel along a track consisting of a single rail , usually one placed high above the ground. ( 10 ) Railroad is very important to the sustainable operation of railway transport.