Daniel is good at English so he has no problems _______...

这道题考查动词的适当形式。在句子‘Daniel is good at English so he has no problems ______ (communicate) with these American friends.’中，‘good at’后面需要跟动词的-ing形式，因此‘communicate’应该变为‘communicating’。这是英语中常见的固定搭配，‘good at doing something’表示擅长做某事。