Step 1: Understand the question.
We must find the biggest weak point of online teaching when we compare it with normal classroom teaching.
Step 2: List what online teaching does well.
Online classes are flexible in time, they offer recorded lectures that students can replay, and they use many multimedia tools like videos and slides. These are clearly good points, not weaknesses.
Step 3: Cross out the strengths.
Multimedia tools, recorded lectures, and flexible timing are all benefits. A limitation must be something the online mode loses, so none of these three can be the answer.
Step 4: Think about what a screen cannot give.
In a real classroom the teacher and students sit together. They see each other, read body language, and react at once. Online, this direct contact is cut down a lot.
Step 5: See why reduced contact matters.
Less face-to-face contact means slower feedback, weaker personal bonding, and harder doubt clearing. This is a true drawback of the online mode.
Step 6: State the conclusion.
The main limitation of online teaching is the loss of direct personal contact.
\[ \boxed{\text{Reduced face-to-face interaction}} \]