Step 1: Ascorbic Acid Overview.
Ascorbic acid is Vitamin C, a vital nutrient functioning as an antioxidant and immune enhancer. Abundant sources include guava, citrus fruits, and amla.
Step 2: Fruit Comparison.
- Winter guava: High in Vitamin C, approximately 200 mg/100 g, but not the peak source. - Acid lime: A citrus fruit providing about 50 mg/100 g of Vitamin C. - Sweet orange: Offers moderate Vitamin C levels, ranging from 40–60 mg/100 g. - Aonla (Indian gooseberry): An exceptionally potent source, containing 600–900 mg/100 g, making it the highest among common fruits.
Step 3: Determination.
Consequently, Aonla is identified as the fruit with the highest concentration of ascorbic acid from the options provided.
Final Answer: \[\boxed{\text{Aonla is the richest source of ascorbic acid (Vitamin C).}}\]