Поставьте глаголы в пустых строчках ...
(is или are)
Arthur ... climb a big tree his mother, Emma ... paint a picture. William ... work in the garden and the cat ... sleep. Everybody ... have a great time

везде is, кроме последнего предложения там are.

Arthur is climbing a big tree his mother, Emma is painting a picture. William is workngi in the garden and the cat is sleeping. Everybody is having a great time