No one has _____ been able to trace the author of the poem.
--- I ____ so busily recently that I ____ no time to help you with your maths.---That’s OK. I can manage it by myself.
I felt _____ to see her _____ face.
There is ____ Mr. Smith at the door who wants to speak to you.
At a rough estimate, Nigeria is ____ Great Britain.
Besides this, it also provides ______ other choices for its readers.