Step 1: Understanding the question.
The question seeks to identify the individual regarded as the pioneer of Christianity among the Garo community — referred to as Kristian Toromko Ra'chenggipa (the one who brought Christianity).
Step 2: About Tangkhan K. Sangma.
Tangkhan K. Sangma is historically known as the pioneer of the Christian religion among the Garo people. His contributions led to the establishment and spread of Christian beliefs in the Garo Hills region.
Step 3: Analysis of options.
- (1) Tangkhan K. Sangma: Correct; known as the pioneer of Christianity in Garo history.
- (2) Omed W. Momin: A Christian leader, but not the pioneer.
- (3) Ramke W. Momin: A later church contributor.
- (4) Gilbert G. Momin: Not associated with the introduction of Christianity.
Step 4: Conclusion.
Therefore, the correct answer is (1) Tangkhan K. Sangma.