请问这句话的语法结构?The radio station received the largest number of calls from listeners on the evening it aired a discussion of the music of James.请问on the evening怎么直接来it了?不懂的不要乱说,如果厉害,

请问这句话的语法结构?
The radio station received the largest number of calls from listeners on the evening it aired a discussion of the music of James.
请问on the evening怎么直接来it了?
不懂的不要乱说,如果厉害,