Step 1: Recall what allicin is.
Allicin is a sulfur-containing compound formed when garlic is chopped or crushed. It is responsible for garlic’s distinctive smell and many of its medicinal properties.
Step 2: Analyze each option.
- (A) Grape → contains resveratrol, not allicin.
- (B) Cauliflower → contains glucosinolates, not allicin.
- (C) Garlic → rich in allicin, formed enzymatically from alliin by the enzyme alliinase.
- (D) Chilli → contains capsaicin, not allicin.
Step 3: Conclude.
Hence, the source of allicin is Garlic.
Final Answer:
\[
\boxed{\text{(C) Garlic}}
\]