Sneezing will intensify the symptom of inflammatory headaches because it will enlarge ______.

the amount of blood in the head

解析：the amount of blood in the head 解析：由题干中的the symptom of inflammatory headaches和Sneezing定位到第三个小标题第2点的末句The pain is heightened by sneezing…that increases the amount of blood in the head．此处需填入名词性成分。题目中的intensify和原文中的heighten同义：题目中的enlarge和原文中的increase也是同义词，所以原文中increase的宾语部分就是答案。