In this questions, two sentences I and II are given. Each sentence has blank in it. against each five options are suggested. Out of these, only one fits at both the places in the context of each sentence. Mark the option as your answer.
Parents are expressing their dissatisfaction to someone else(but not with children) ,so we need to use a negative word . Hence,B is eliminated . C is too broad in nature, as parents never protest against their children. A and D mean the same.But, the sentence is clearly ought to express Parent's dissatisfaction against children ( to someone else)hence,complain is the best fit.