题目内容：

will Jack spend with his grandparents?a:how farb:how long c:how soon d:how much

优质解答

(B.How long) will Jack spend with his grandparents?
杰克将要和祖父母一起过多长时间?
因为谓语动词是spend（度过）,所以疑问词应该是跟时间有关的,问时间的长短.