(Thirteen hundred) medical professionals, (all of which) have been trained to treat drug dependency, (attended) the annual convention (sponsored) by a society.

A．bats destroy crop-damaging insects
B．bats are the marvel of evolution adaptation
C．bats suck the blood of dying people
D．bats inspire disgust based on some traditional beliefs

A．he lost his self-confidence
B．he was mentally retarded
C．his teacher had little confidence in him
D．his parents expected too much of him