Cast iron kettlebells differ from competition kettlebells primarily in that:
A. They have no handle and require two-handed gripping
B. They should not be used for explosive training movements because of their increased risk of injury
C. They have variable dimensions across different weights and handle diameter changes as weight increases
Answer in the poll, then explain your rationale below in the comments! I'll follow up with my breakdown of the question after enough people have responded.
From Chapter 16: Exercise Technique for Alternative Modes and Nontraditional implement Training