________ all of them are strong candidates, only one will be chosen for the post.[ ]

We have an adviser on hand in this activity ______ you have any worries or problems.

surprise, my good friend _________stay up to study to prepare for the next important exams organized by tenfamous high schools.

He has made another wonderful discovery, _____ I think is of great importance to science.

“A ______ accident happened at 7:30 a.m.” said the policeman _______.