+++ ～か？ It is only a question. +++ Aするのか？ The questioner thinks that you should not do A, or A is unlikley to happen お前もいくか？　Will you go, too ? / Do you want to go, too ? お前もいくのか？　Will you really go ?/Do you really want to go? ( I hope you do not ) OK: 握り飯だ。食うか？　Here is a a rice ball. Do you want to eat this? NG: 握り飯だ。食うのか？　 OK: それ、三日前の握り飯だぞ。（本当に）食うのか？ 　　　　　　　　　　　　　 OK: それ、虫だぞ。本当に食うのか？ It is a bug. Will you really eat that? >病気の母親にも、そんなにそまつな飯を食わせているのか？ The questioner thinks that it is unlikely to/should not happen.

I think this site will help you understand http://www014.upp.so-net.ne.jp/nbunka/00oct.htm No.1-C is showing about のか in this case. の　is mainly used by women in a gentle way of asking.(if you use it when you are asking) So it is quite strange to say together with the words such as "母親" "そまつ"　"飯" "食わせる" . But still it makes sense. if you use just か in this sentence, it's also quite strange. Actually it's worse than just saying の. Japanese can get the meaning, but it is not correct. If you're use 'か’　in asking something , it usually come with ( noun + です) or (verb/noun + でしょう)　or (verb + ます) or　(verb +ました).