The primary vector that helped carry zebra mussels into the Great Lakes was:
D. ship ballast
Explanation:
1. Ship ballast refers to the water or material used to stabilize ships.
2. Zebra mussels were unintentionally transported in ballast water of ships from their native European waters to the Great Lakes.
3. This transportation allowed zebra mussels to spread and establish populations in the Great Lakes, causing ecological and economic issues.
