They went up the CN tower and looked across the shores of Lake Ontario. Standing in the distance, they were ________ to see misty clouds rising from the great Niagara Falls, which is on the south side of the lake. _________ and splendid water from the lake flows into the Niagara River and over the falls on its way to the sea, forming a picture of __________.(astonish) (所给词的适当形式填空)