Parents always _________ great importance to education. They will do their best to give their children that priceless gift.

Have you ever wondered why some of the smartest students in your class sometimes ________ failing exams? 

I forgot his phone number that day.I had to ___ the phone book to find it. 

Wang Hong is considered ___ one of the best students in our grade.

．Our teacher is very busy.He is ________ in working out a teaching plan.