Sentence:  `` Comment '' ? ejaculated the surprised woman , looking at Alex for an <WSD>explanation</WSD> but he , parting from her without ceremony , only offered a few words about the doctor 's provincial American speech and a state of nerves brought on by the demands of his work . 
Meaning of the word marked with <WSD> tags:  a statement that makes something comprehensible by describing the relevant structure or operation or circumstances etc.