Nutritionists and global health organizations, such as the Indian Council of Medical Research (ICMR), provide specific dietary guidelines for maintaining optimal health. For an average adult, a daily intake of at least 100 grams of fruits is generally recommended to ensure a sufficient supply of vitamins, minerals, and antioxidants.
Step 1: Analyze the options.
(A) 50 grams: This amount is generally considered too low to meet the daily requirements for essential micronutrients found in fruit.
(B) 100 grams: This aligns with standard nutritional guidelines in many agricultural and health textbooks (particularly in the Indian context) as the minimum recommended daily serving.
(C) 200 grams: While consuming more fruit is often healthy, 100g is typically cited as the primary "stay healthy" benchmark in standard curricula.
(D) 300 - 400 grams: This range is more typical for total vegetable intake or combined fruit and vegetable targets, rather than fruit alone.
Step 2: Conclusion.
Based on standardized nutritional recommendations for dietary health, 100 grams is the recognized target for fruit consumption. Hence, the correct answer is (B).
Final Answer:
\[
\boxed{(B) \, 100 \text{ grams}}
\]