D.
A billion days ago no-one walked on the earth on two feet.
They got that one badly wrong
A billion days ago is 2.74 million years ago; human ancestors started being bipedal around 4 million years ago
And that's not counting bipedal dinosaurs, of which there were plenty
A.
A billion seconds ago it was 1959.
That one's wrong, too
A billion seconds is 31.7 years, so that'd be about the end of 1979.
B.
A billion minutes ago Lord was alive.
Only if Lord was alive in 110 AD
Well of course some people believe that (and think he's still alive even now), so we'll let that one pass
C.
A billion hours ago our ancestors were living in the Stone Age.
114,000 years ago, so OK, that one's correct