A middle school teacher gives her students the following question: 'In the given expression what number do you think belongs to the box? 9 + 3 = [ ] + 7.' The common responses of her students were 12 and 19. Which of the following statements is most appropriate for the given context?

A mathematics teacher of Class II gives the following word problem on addition to the students: 'A bag contains 4 mangoes and 6 more mangoes are put into it. How many mangoes are there in the bag in total?' This type of word problem belongs to which of the following structures of addition?

A teacher wrote the number 308 on the blackboard and asked the children to read it aloud. A child said, 'It is thirty-eight.' Which of the following is the most appropriate strategy to rectify the error made by the child?