I think _______ our duty to keep our environment clean and tidy.

While he was investigating ways to improve the telescope, Newton made ________ discovery which completely changed ________ man’s understanding of color.

This city isn’t the same_____ that one. They are different_____ each other.[ ]

_____Greens are preparing for the coming Thanksgiving Day.

Good news. We will have aholiday. . —I’ve heard of it. But it’s coming in .