Mary _______ her mother with the housework, but she didn’t.
It was my sister first had the idea to cycle along the entire Mekong River from ______ it began to where it ends.
In fifteen terrible seconds a large city .
---My family usually goes skating for vacation. I like skating, but I want to try something different this year. ----_______.
Not easy as the problem of pollution is____, no one should just stop trying.
Let us suppose that we _____him about it, what would have happened?