I'd appreciated hearing from you ____ telling me how everyone is getting along选择题这里该写什么
题目As I'll be away for at least a year, I'd appreciated hearing from you ____ telling me how everyone is getting along
选项A. sometimes, B. often, C. always, D. now and then
这里答案选D,但是我看不出前面几个有什么错,求指教.