【题目】Raising a child can be _______, but it is well worth it.
A. over the moon B. a piece of cake
C. on its last legs D. a Herculean task
在线课程【答案】D
【解析】
考查习语。A. over the moon欣喜若狂；B. a piece of cake小事一桩；C. on its last legs奄奄一息；D. a Herculean task一项艰巨的任务、沥尽心血。句意：抚养孩子虽然很费心血，但是很值得。根据句意可知此处表示“沥尽心血”，故D项正确。