Step 1: Plan:
I will think about when the technical rehearsal happens and what the team does there, then match the options.
Step 2: Timing:
It takes place just before the first public show, after the actors know their lines.
Step 3: Work done:
The crew runs every light, sound and set change in order and notes the faults.
Step 4: Match the options:
Replacing dialogue and designing costume are not part of this work. Creating mood is a design goal, not the purpose of the rehearsal. Fixing glitches matches the work.
Step 5: Conclude:
Option 4 is the answer.
Final Answer:
The answer is option 4, Overcome the technical glitches before the public show.
\[\boxed{4}\]