(2012·安徽) A lot of language learning, __________ has been discovered, is happening in the first year of life, so parents should talk much to their children during that period.
Nobody knows how the accident _________. The police are investigating it.
I tried to telephone Mary last night, but I couldn’t ________ after trying again and again.
History is the best teacher. It _________ records the development of every period, whether it is good or not.
The decision to inspect the middle school is _______ so that they can see the true situation of both teachers and students.
The cruel reality was ________ for him, so he decided to go on a beach vacation to relax and think about what he should do next.