Teaching will be least effective when :

Concept: Teaching-learning is effective only when it functions as a two-way, learner-centred process - the teacher facilitates rather than dictates, learners participate actively rather than merely receive, and instruction develops the full range of skills the objective demands rather than a single skill in isolation.

Application: Each of the following independently interrupts this process:

• An autocratic teacher removes two-way communication - the lesson becomes teacher-centred, leaving no room for learner questions, feedback, or initiative.

• Passive learners do not construct meaning through questioning, discussion, or practice - without active participation, information does not convert into durable learning.

• An emphasis confined to writing alone neglects listening, speaking, and practical/psychomotor skills, so instruction serves only one dimension of the learning objective.

Cross-check: these three conditions are not mutually exclusive, and each is independently documented in teaching-aptitude literature as a barrier to effective teaching on its own - a classroom is not restricted to showing only one of them at a time. Since the question asks under which condition(s) teaching becomes least effective, and each condition independently satisfies that criterion, the option that names every one of them together is the complete response.