根据句意，写出括号内所给单词的适当形式。
There are smaller and older teaching buildings in our school than those in _________(they)
Qi Baishi’s Chinese ________________ (paint) sell well now .
Mary is very ____________(help) and often helps others .
September is the ____________ (nine) month of a year .
Christmas Day is one of the __________( west) festivals.