I know you didn’t break the window. It ............ by Emma’s sister.

In which sentence is CAPITALIZATION correct?

Children can fly alone on international flights ..................... they’re at least six years old.

There’s something wrong with the window. It just ...................... open.

If Mrs. Hill finishes writing her new book, she .................. with her family.

I don't know how...... to answer that question. It was very easy.