e waters of this great lake, whichis also the world’s deepest, have been ____ by waste from a chemical factory

getting dark earlier than before,isn’t it— Yes. I think so. I see ____ is onalready.

My room gets very cold at night.—___________.

Without proper lessons, you could ________a lot of bad habits when playing the piano．

____________better ways for digging tunnels__________,the first railway tunnel under the River Thames was dugin 1884.