He was reading his book, completely _______ to the world.
Only after my friend came______.
Though difficult, I ________ him find a job, which made him very pleased.
We are faced with the problem _________ we should do with so much pollution.
The naughty boy spends most of his time playing computer games ______ his lessons.
——Thank you for showing me the way! ——____________. I live nearby, so I am familiar with this area.