(A) brown recluse spiders are rarely fatal, they cause chronic flesh wounds, posing the greatest danger to the infant and elderly, who are particularly vulnerable to its

(B) brown recluse spiders are rarely fatal, they cause chronic flesh wounds and pose the greatest danger to the infant and elderly, who are particularly vulnerable to their

(C) the brown recluse spider is rarely fatal, it causes chronic flesh wounds, posing the greatest danger to the infant and elderly, who are particularly vulnerable to their

(D) the brown recluse spider is rarely fatal, it causes chronic flesh wounds and poses the greatest danger to infants and the elderly, who are particularly vulnerable to its（D）

(E) the brown recluse spider is rarely fatal, they cause chronic flesh wounds, posing the greatest danger to the infant and elderly, who are particularly vulnerable to its

我觉得Ｄ中的ＩＴＳ不对，应该是spiders的poison.，故我选Ｃ．请各位高人指点

恩，根据OG的解释，这里的poison的主语应当是bite，其实第一次我也觉得是spiders。虽然从感觉上来说spiders更正确一点。但是我记得在OG11th补充材料里面有一道题（没记下来），就是说这里，their是不能指回spiders的，因为他们bite的物主代词。所以就选D了。

请高人们指正。