单选题 Each time he heard the approaching ______ of his mother, he would turn off the light and feigned (佯作) sleep.
【正确答案】 D
【答案解析】[解析] 名词词义辨析。能与空格前后的heard，his mother，构成名词的只有footstep，意为“听到他妈妈的脚步声”。故答案为D。