Which of the following is not desirable with respect to carrying out of a…

A classroom demonstration works best when it follows the inquiry-based (discovery) approach to teaching: the teacher's job is to prepare the activity carefully, present it clearly, and help students consolidate what they observed - while the students themselves watch, question, and work out the required connections on their own. Handing over the intended conclusions before the observation even begins removes this active-discovery element and turns the demonstration into a passive confirmation exercise instead.

Among the four practices listed, three directly support this discovery-oriented approach: rehearsing the demonstration beforehand lets the teacher confirm timing, materials and steps so it runs smoothly and safely; supplementing it with explanation while it unfolds helps students correctly interpret what they are observing; and following it up with discussion afterward lets the teacher check and consolidate the connections students actually drew for themselves. Announcing the specific linkages students are required to make before they even observe the demonstration, however, tells them the conclusion in advance - they no longer need to watch and infer it themselves, which defeats the very purpose of carrying out the demonstration. This is the one practice that is not desirable.

• Rehearsing beforehand is preparation for smooth, safe delivery - it does not disclose any conclusion to students, so it remains desirable.

• Supplementing with explanation clarifies what is being observed as the demonstration happens, without pre-empting the students' own inference - also desirable.

• Following up with discussion checks and reinforces understanding only after students have already engaged with the demonstration - again desirable.

This reading is confirmed by the official CTET (January 2024, Paper 2) answer key, which marks pre-announcing the required linkages as the undesirable practice among the four options.