Deep levels of the group II and III elements Zn, Ga, Cd, and In are investigated. By using radioactive impurities as a tracer, the assignment between a band gap state and a certain element is either established or ruled out definitely. By means of Deep Level Transient Spectroscopy on p-type SiC, one Zn- and two Cd-related band gap states are identified. In contrast to proposals based on magnetic resonance experiments, there is no deep level of the group Ill elements Ga and In in the lower part of the band gap. In particular, these elements do not contribute to the formation of the known D-center.