Final answer:
The lecture format is widely regarded as the least effective in terms of student engagement and retention, yet it remains the most widely used due to its convenience and prevalence in education systems.
Step-by-step explanation:
The least effective but most widely used education meeting format is c) Lecture format. Although the lecture format allows instructors to deliver information to a large audience, it is generally considered to be the least effective in terms of student engagement and retention of information. Studies and education experts point out that active learning strategies, such as hands-on training or participatory discussions, tend to result in better understanding and retention of the material. However, due to its convenience and traditional prevalence in education systems, the lecture format remains the most widely used.