All are exploring instruments for a root canal except:: (A) DG-16, (B) JK-17, (C) CK-17, (D) JW-17
Answer is B. The DG-16 endodontic explorer is used to identify canal orifices and to determine canal angulation.
The CK-17 endodontic explorer serves the same purpose, but it's thinner, stiffer tip can be useful for identifying calcified canals.
Micro JW-17 - Thin Canal Explorer, Double-Ended, Single instrument.

JK-17  - Dental explorer or sickle probe.