morphemes 词素,即单词意思的最小单位
例如:
desire----------------one morpheme
desire+able-----------two morphemes
desire+able+ity-------three morphemes
un+desire+able+ity----four morphemes
再看看题中,finger明显就只有一个
disgraceful -----dis+grace+ful 3个
stepsister ----step+sister2个