Doctors still know little about how the Listeria bacterium is spread and why the disease it causes, listeriosis, afflicts some people in a contaminated area though it spares many others. (A) though it spares (B) where it spares (C) despite sparing (D) when sparing (E) while sparing listeriosis和disease是同位语;it cause做disease的定语,it 指代the Listeria bacterium ,意思是由bacterium引起的这种疾病。