When a Trademark application is objected by the trademark department on relative grounds of refusal or absolute grounds of refusal then a reply is required based on legal and reasonable grounds of registration.
It is important to note that there is a difference in Trademark Objection and Trademark opposition. Trademark opposition is filed by other party or third parties once the trademark application is accepted by the trademark department and advertised.
For reply to Trademark objections, you need to prepare valid, legal and reasonable ground in support of your application. A formatted reply may send your application for hearing proceedings which takes years in registration.