Nambiyandar Nambi, the famous scholar who arranged the Saiva canons, was a contemporary of Rajendra I. Let's understand this in detail:

Nambiyandar Nambi:
- Nambiyandar Nambi was a renowned scholar and devotee of Lord Shiva who lived during the 10th and 11th centuries.
- He played a pivotal role in preserving and arranging the Saiva canons, which are sacred scriptures of the Saiva Siddhanta philosophy.
- Nambi's work involved organizing and systematizing the hymns and teachings of the Nayanars, the poet-saints of Tamil Nadu who composed devotional poems dedicated to Lord Shiva.

Saiva Canons:
- The Saiva canons are a collection of religious texts that form the basis of the Saiva Siddhanta philosophy.
- These texts include the Tirumurai, which is a compilation of hymns composed by the Nayanars, and various other scriptures that expound on the philosophy, rituals, and practices of Shaivism.
- Nambi's efforts in arranging the Saiva canons ensured their preservation and accessibility for future generations.

Contemporaries of Nambiyandar Nambi:
- Rajendra I was the son of Rajaraja I, the famous Chola emperor who ruled during the 10th century.
- Rajendra I succeeded his father and became the Chola king in 1014 CE.
- Nambiyandar Nambi and Rajendra I were contemporaries, meaning they lived during the same period of time.
- It is believed that Nambi had a close association with the Chola court and had the patronage of Rajendra I.

Explanation of the Correct Answer:
- Among the given options, Rajendra I is the only contemporary of Nambiyandar Nambi.
- Rajendra II, Prantaka I, and Rajaraja I are not contemporaries of Nambi.
- Rajendra II succeeded Rajendra I and ruled during the 11th century, after Nambi's time.
- Prantaka I and Rajaraja I were rulers of the early Chola dynasty and lived before Nambi's time.

Therefore, the correct answer is option A, Rajendra I.