Why is the Rajya Sabha called the permanent House of the Parliament?

The correct answer is Option 2 - Because it never dissolves completely

The Rajya Sabha is called the permanent House of the Parliament because it is never fully dissolved; every two years, only one-third of its members retire and are replaced.

Members of the Rajya Sabha are elected for a term of six years. They can get re-elected. All members of the Rajya Sabha do not complete their terms at the same time. Every two years, one third members of the Rajya Sabha complete their term and elections are held for those one third seats only. Thus, the Rajya Sabha is never fully dissolved. Therefore, it is called the permanent House of the Parliament. The advantage of this arrangement is that even when the Lok Sabha is dissolved and elections are yet to take place, the meeting of the Rajya Sabha can be called and urgent business can be conducted. Apart from the elected members, Rajya Sabha also has twelve nominated members. The President nominates these members. These nominations are made from among those persons who have made their mark in the fields of literature, science, art and social service.