Step 1: Idea:
Look for the polyester among the common polymers.
Step 2: Fact:
Dacron, also called terylene, is polyethylene terephthalate (PET), a polyester.
Step 3: Rest:
The other three have no ester group.
Final Answer:
Dacron is polyethylene terephthalate, a polyester.
\[ \boxed{B} \]