It is dark outside, so please____ your step while going down the stairs.
The tall buildings are _________ in the lake aroundwhich there are many trees.
He had been so absorbed __________ watching the carpassing by that he didn't notice his friends __________.
According to a UN report, some 844 animals and plants __________ in the last 500 years.
—Have you finished the book? —No. I've read up to __________ the children discover the secret cave.
When I opened the door, I found my father sitting in his chair, completely __________ in the humorous stories he was reading.