[解析]
解:∵当x∈A时,若有x﹣1∉A,且x+1∉A,则称x为A的一个“孤立元素”,
∴单元素集合都含孤立元素,
S中无“孤立元素”的2个元素的子集A为{0,1},{1,2},{2,3},{3,4},{4,5},共5个
S中无“孤立元素”的3个元素的子集A为{0,1,2},{1,2,3},{2,3,4},{3,4,5},共4个
S中无“孤立元素”的4个元素的子集A为{0,1,2,3},{0,1,3,4},{0,1,4,5}},{1,2,3,4},{1,2,4,5},{2,3,4,5}共6个
S中无“孤立元素”的5个元素的子集A为{0,1,2,3,4},{1,2,3,4,5},{0,1,2,4,5},{0,1,3,4,5},共4个
S中无“孤立元素”的6个元素的子集A为{0,1,2,3,4,5},共1个
故S中无“孤立元素”的非空子集有20个
故选:D.