There was no need to introduce it. 
It's introduction was not necessary.
Introducing it was very import and and was a must.
The ones that require the full day to complete will often require a packed lunch.
They are educating others.
His shirt has no decorations.
I don't think he's here.
A group of children are swimming in a blue creek.
We were the first ones to make those but we left the business in 1981.