Điền vào chỗ trống với 1 giới từ phù hợp:
Gangnam Style, by a 34-years-old South Korean singer, PSY, first appeared................... Youtube in July.I bought some souvenirs..................... my friends when I was in Nha Trang.Fiona is getting better and better ...................... writing compositions.Our country is rich .................. oil and rubber.The school cafeteria only opens ...................... lunchtime.My mother is very keen ..................... growing roses.The science books are................. the rack .................. the corner of the room.I am 13 years old now. I prefer to talk................. people................. my age.