Question

Tick the passive sentences in which you can omit the agent

Answer 1

The fashion show was watched by thousands of people. No se omite.
 
High heels are often worn on especial occasions. √
Se puede omitir (by women) porque los tacones suelen llevarlos las mujeres. el agente es obvio.

My wedding dress is being delivered tomorrow.  √
Se puede omitir el agente (by the company) , el principal de la oración es que se entrega mañana.

My suit was cleaned.  √
se puede omitir el agente (by the dry cleaner´s) no es importante o relevante  para que se entienda la oración.