Потрібно поставити речення в трьох формах The perfect tense
1.His parents enjoed travelling by sea last July
2.Susan usually travels by bus or train
3 Her friends travelled by bus round Europe last year
4.They have just arrives

1. His parents have never enjoyed travelling by sea. - Present PerfectBy that time his parents had already enjoyed travelling by sea. Past PerfectBy Christmas his parents will have enjoyed travelling by sea. - Future Perfect2. Susan has never travelled by train. - Present PerfectSusan had travelled by bus. - Past P. (=Perfect)By the end of the month Susan will have travelled by train. - Future P3. Her friends have just travelled by bus round Europe. - Present PBy that time her friends had just travelled by bus round Europe. - Past P.By the end of the week her friends will have travelled by bus round Europe. - Future P.4, They have just arrived. - Present P.By that time they had already arrived. - Past P.They will have arrived by the end of the week. - Future P.