This is explained on our Relative clauses page -- see the section called Omitting the relative pronoun. Could you please have a look there? If you have any other questions after reading that, please don't hesitate to ask us again.
When I need to go out, I take my rucksack and put my mobile phone, house keys and wallet in it. I don't need a lot of stuff in my rucksack because I don't like to take too much with me.
It can depends for what reason I go out. If I just go out to walk or to go to the market for example, I just bring my mobile phone, keys and my wallet. If I go out to work, I carry in additional my briefcase which contains my laptop, my glasses and my papers work.
Hello Tran Ngoc
This is explained on our Relative clauses page -- see the section called Omitting the relative pronoun. Could you please have a look there? If you have any other questions after reading that, please don't hesitate to ask us again.
All the best
Kirk
The LearnEnglish Team