Is that his class？怎麼變成複數形式？

Are those their classes？

RELATED INFORMATIONS

1. 句型轉換.1.This is a pencil- box.（改為複數句）_______ ______ ______pencil-boxes. 2.Are you Miss Gao？（做否定回答）____，____ ____.3.The twins come from Japan.（改為同義句）The twins ____ ____Japan.4.I don't know how I can look after my dog.（改為同義句）.I don't know how ____ ____ ____my dog.5.Mr Green is from __the USA__.（對劃線部分提問）____ ____Mr Green ____？
2. this is a pencil改為複數句
3. This is my pencil（變為複數句）
4. 將下列句子變為複數句Is this a new shoe？Is that a pencil_box？She doesn't work on Subday It is not a watch. The child is singing happily.
5. is that a box改成複數
6. That is his brother的複數形式
7. It is a photo（改為複數句）
8. 完成句子1.This is a photo.（改為複數）_______ _______ ________photo 是_________ _____________photo.
9. this is a bus.【變為複數句】
10. whose coat it is？
11. That is his book.怎麼改為複數句
12. that is his brother改為複數句
13. that is a pencil.改為複數句
14. 不可數名詞是不是永遠都不可能用複數形式.（-s）比如水，永遠都不會出現waters這種情況？還有”cloud”是不是可數名詞，我覺得是不可數，但怎麼新概念第一册書上有”There are some clouds in the sky，but the sun is shining.”
15. suggestion有複數形式麼還是不可數名詞？
16. 沒有複數形式的都是不可數名詞嗎？不可數名詞可用are修飾嗎
17. “不可數名詞通常沒有複數”怎麼理解？
18. That woman is a teacher改為複數句
19. woman teacher變複數？
20. she is a woman teacher.（改為複數句）