His shoes are muddy. He        be working in an office all day.

 One of our rules is that every student ____ wear school uniform while at school.

Tigers like to eat _____________, but koalas like to eat____________.

--- The fog is so thick that the express way ____ have been closed. --- You are right. I ____ have thought of that. Now we have to take another road.

Please remind your grandpa to take medicine on time, for a man of his age ____be very forgetful．