Some people are worrying about the possibility ________ mobile phones could be responsible for a range of illnesses, from rashes(皮疹) to brain tumors．

Oh, you are so clever! You have______ a solution to the difficult problem!

Tom went to his teacher for ______ on how to work out the problem.

They want to develop a kind of dog-friendly food _____ will help dog owners cool down their pets. [ ]

Your bedroom is too dirty, please _______.