Compared to Ida, Eros, and Gaspra, What Was Odd About

Compared to Ida, Eros, and Gaspra, what was odd about Mathilde?

A) It had a small moon, so we could more accurately find its mass.
B) It was much denser, probably made of iron and nickel, a class M asteroid.
C) It was less dense than water, indicating it was a comet nucleus, rather than an asteroid.
D) It was less dense than rock, but more than ice, suggesting a porous structure.
E) It was the same density as the Earth's Moon, indicating it had been knocked off our Moon.