Legal Question in Real Estate Law in California

You don't. You have to file an Answer specifically drafted for your case.

The Judicial Council provides a wide array of general-purpose forms for court filings in relatively routine matters, and/or for use by people representing themselves. Eminent domain proceedings are not among those covered by any general-purpose form. Attempting to provide such a form would entrap people into making mistakes and omissions, and would produce a confusing record for the court to work from. I recommend retaining, or at least consulting with, a lawyer with significant experience in eminent-domain matters. Unless the land, etc. to be taken from you is of very little value, you'll want and need expert assistance.

You need to hire an eminent domain lawyer. Don't try to do this with legal help. I can refer you to one.