Final answer:
The safest position when preparing for an unprotected left turn in traffic is to keep wheels straight to avoid being pushed into oncoming traffic if rear-ended.
Step-by-step explanation:
When waiting to make an unprotected left turn in heavy traffic, the best position to take is to keep your wheels straight. This is the safest option because if you are hit from behind, having your wheels straight will prevent you from being pushed into oncoming traffic. Hence, the correct answer to this question is D) Keep your wheels straight.