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.
Not until all the fish died in the river ____________ how serious the pollution was.
If he ___________ my advice then, he would not be in trouble now.
It doesn’t matter ___________ you turn right or left at the crossing — both roads lead to the park.
It was in the school __________ he had studied ___________ he began the important experiment.
I felt somewhat sad and was about to leave _________ something happened which drew my attention.