"Wisdom" by Sara Teasdale

It was a night of early spring,
The winter-sleep was scarcely broken;
Around us shadows and the wind
Listened for what was never spoken.
Though half a score of years are gone,
Spring comes as sharply now as then--
But if we had it all to do
It would be done the same again.
It was a spring that never came;
But we have lived enough to know
That what we never have, remains;
It is the things we have that go.

What is the rhyme scheme of the poem?
-ABAB

-ABCD

-ABBA

-ABCB