Constructivist classrooms focus on student questions and interests, they build on what students already know, they focus on interactive learning and are student-centered, teachers have a dialogue with students to help them construct their knowledge, they root in negotiation, and students work primarily in groups. Role of teacher in a constructivist classroom:facilitate the learning of students and assist them only when needed otherwise provide freedom for students to construct knowledge on their own.make the environment of the classroom comfortable for children where they feel secure and wanted.the steps for learning are worked out jointly by the child and the teacher, based on the child's understanding and the teacher's knowledge. Through hints and suggestions encourage the student to build upon the conceptual structures that she/he has already built in her mind.the teacher should not curtail students' autonomy by presenting ready-made solutions to/him.encourage students to explain what they know and what they feel.?Hence B & D are the correct options. Additional InformationOn the other hand, reading & explaining knowledge or asking questions and explaining doesn't describe the role of the teacher in a constructivist classroom as the student remains a passive recipient of knowledge here.