Concept:Constructivist teaching encourages children to explore, hypothesize, and generalize from hands-on activities rather than receiving direct answers.Explanation:The teacher should not simply tell the reason (density) or postpone the explanation. Instead, he should let each child observe freely, record findings, and interpret them. This builds personal understanding. Then, each child should hypothesize why objects float or sink, test their ideas, and form generalizations from the activity. This develops scientific thinking and inquiry skills. Directly giving the answer (option A) or delaying it (option D) does not engage children in active learning. Therefore, the most appropriate actions are (B) and (C).Answer:Option A: (B) and (C)