Which sentence contains an error in punctuation?

a) (d)what was the object that nerved us, or those who went before us, to this choice?

b) (a)we have gathered here to affirm a faith, a faith in a common purpose, a common conviction, a common devotion.

c) (b)some of us have chosen america as the land of our adoption, the rest have come from those who did the same.

d) (c)for this reason we have some right to consider ourselves a picked group, a group of those who had the courage to break from the past and brave the dangers and the loneliness of a strange land.