中间应该是逗号不好意思打错了，那你能讲解下吗？选A 由于他把注意力放在小说上了,所以没注意老师来了.-ed 表原因,与后面的he一致,表被动.如果用to do形式,就是表目的了.如:To fix his attention on his novel ,he used a pen to write on it.他为了把注意力放在小说上,就拿了支钢笔在上面画.原句若用-ing形式应为;Fixing his attention on the novel,he didn't notice the teacher coming.