用who,whom或which把以下每对句子改写成一句话.
1.Thisistheticket.Iboughtityesterday.
2.Thegirlisstandingbesidethewindow.Sheisanewstudent.
3.Therearethepresents.Iboughtthemformyparents.
4.Thecarisexpensive.Hecan'taffordit.