For at least half of that time, those cells didn't have a nucleus.
The cells do not have a nucleus for at least some of the time.
All cells have a nucleus at all times.
When customs agents questioned Jeb Bush's wife, she lied.
I have never been to Virginia.
a man is cooking
Things that don't exist include a negative saving rate.
The woman is skiing down Everest.
A man is riding a bike.