Which is __________, traveling by air or by train?
The earth will become worse and worse ________ we do something to stop her from being polluted.
I _______ riding my bike________ taking buses to school.
— Can you come and play football with me?—______. I have a lot of homework to do.
Soft colors like pink and light blue make people _______, so they spend more time _______their meals.
I was late today because alarm clock didn’t _______ .