All of us have been to the park ____________________ because both of you are ill at home.

The book is useful because it gives us advice on how to improve memory.

We are so tired ______ we could take the day off tomorrow!

下列句子中“而”字的用法与例句相同的一项是例句：冰，水为之而寒于水

Thank you, Mille and Kitty. It was kind of you to help me with my lessons. —- _________.