Which sentence has no errors in capitalization?

a.
sarah said, "first, wet the clay." she picked up a lump, dropped it, and said, "then center it on the wheel."

b.
sarah said, "first, wet the clay." she picked up a lump, dropped it, and said, "then center it on the wheel."

c.
sarah said, "first, wet the clay." she picked up a lump, dropped it, and said, "then center it on the wheel."

d.
sarah said, "first, wet the clay." she picked up a lump, dropped it, and said, "then center it on the wheel."