The passage suggests that scientists consider their understanding of gamma-bursts to be
A． incomplete because they still have yet to establish a taxonomy of the various types of GHBs they have observed B． adequate enough to redirect research toward other more perplexing aspects of black holes C． unsurprising, given that scientists have long felt kinetic energy to play a role in the emergence of GHBs D． disappointing because the mechanism by which GHBs become visible is still poorly understood E． in need of confirmation through comparison with another astronomical phenomenon that involves electromagnetic bursts