**Core Concept**
Cannabis indica is a species of cannabis plant known for its high content of THC (tetrahydrocannabinol), the primary psychoactive compound. The potency of cannabis is often measured by its THC content, with higher levels indicating a more potent effect.

**Why the Correct Answer is Right**
The most potent form of cannabis indica is typically extracted from the resinous trichomes of the female plant, specifically the glandular trichomes that contain high levels of THC. The process of extracting these trichomes, often referred to as "hashish" or "charas," results in a concentrated and potent form of cannabis. This concentrated form of cannabis is often smoked, vaporized, or ingested to produce a potent psychoactive effect.

**Why Each Wrong Option is Incorrect**
**Option A:** CBD-rich cannabis strains are not typically considered potent due to their lower THC content and higher CBD content, which is known for its therapeutic effects rather than psychoactivity.
**Option B:** Cannabis sativa is a species of cannabis plant known for its lower THC content and higher CBD content compared to indica, making it less potent.
**Option C:** THC-free cannabis products, such as those containing CBD only, are not considered potent as they do not contain the psychoactive compound THC.

**Clinical Pearl / High-Yield Fact**
The potency of cannabis can vary significantly depending on the strain, growing conditions, and extraction method, with some strains reaching THC levels as high as 30%.

**Correct Answer:** B. THC-free cannabis products