An instructor has just finished teaching a difficult concept to a group of learners. It is necessary for the learners to master this concept before moving on to the next concept. The instructor asks the learners if there is anyone who does not understand the concept and gets no response. Which of the following is the MOST appropriate next step for the instructor to take in this situation?

A.
Begin teaching the next concept, since the instructor can assume from the lack of learner response that everyone understands the difficult concept.

B.
Review the previous concept, since it can be assumed it was during the teaching of that concept that learners stopped responding.

C.
Reteach this concept, since it can be assumed that none of the learners understands the difficult material.

D.
Assess learner understanding of the material, since some learners who do not understand may be unwilling to indicate this lack of understanding.