**Explanation:**

The correct answer is 'A) Sri Lankan Tamils.'

**Sri Lankan Tamils:**
- Tamil natives of Sri Lanka are referred to as Sri Lankan Tamils.
- They are a distinct ethnic group in Sri Lanka and are predominantly Tamil-speaking.
- They have a long history in the country, and their presence can be traced back to ancient times.
- Sri Lankan Tamils are considered one of the major ethnic groups in Sri Lanka, alongside Sinhalese, Sri Lankan Moors, and Indian Tamils.

**Indian Tamils:**
- Indian Tamils, also known as Hill Country Tamils or Upcountry Tamils, are descendants of Tamil laborers brought to Sri Lanka during the British colonial period.
- They were brought to the country to work on tea plantations in the central highlands.
- Indian Tamils are considered a separate ethnic group from Sri Lankan Tamils due to their distinct historical background and cultural practices.

**Muslim Tamils:**
- The term "Muslim Tamils" is not commonly used to refer to a specific ethnic group in Sri Lanka.
- Sri Lankan Muslims, also known as Moors, are an ethnic minority in the country who primarily practice Islam.
- While there are Tamil-speaking Muslims in Sri Lanka, they are not specifically referred to as "Muslim Tamils."

**Conclusion:**
- Tamil natives of Sri Lanka are called Sri Lankan Tamils, as they are a distinct ethnic group with a long history in the country.
- Other terms such as Indian Tamils and Muslim Tamils refer to different ethnic groups within the larger Tamil community in Sri Lanka.