Step 1: Understanding the religious composition of India.
According to Census data, the major religious communities in India include Hindus, Muslims, Christians, Sikhs, Buddhists, and Jains. Among these, Hindus form the majority, followed by Muslims, Christians, and Sikhs.
Step 2: Checking the given options.
- (A) Muslims → They form the largest minority group (about 14%).
- (B) Sikhs → Around 2% of the population, larger than Buddhists.
- (C) Christians → Around 2.3% of the population, also larger than Buddhists.
- (D) Buddhists → Around 0.7% of the population, making them the smallest among the given groups.
Step 3: Conclusion.
Therefore, Buddhists are the smallest religious group in India among the options given.
\[
\boxed{\text{Buddhists}}
\]