They are building a new recycling centre in our town.
BUILT
A new recycling centre .................... our town.
I am sure the factory has been polluting the river for years.
MUST
The factory .................... the river for years.
We could not go hiking because the weather was so bad.
TOO
The weather was .................... to go hiking.
It was only after the flood that the government took action.
UNTIL
It was .................... that the government took action.
Scientists started researching climate change decades ago.
BEEN
Scientists .................... for decades.
I would prefer you not to throw plastic into the sea.
SOONER
I would .................... throw plastic into the sea.