Step 1: Classify vitamins.
Vitamins are broadly classified into two types: water-soluble and fat-soluble.
Step 2: Identify water-soluble vitamins.
Water-soluble vitamins include:
Vitamin B-complex and Vitamin C.
Step 3: Identify fat-soluble vitamins.
Fat-soluble vitamins include:
Vitamins A, D, E, and K.
Step 4: Analyze given options.
Vitamin C → Water-soluble
Vitamin E → Fat-soluble
Vitamin A → Fat-soluble
Vitamin D → Fat-soluble
Step 5: Conclusion.
Only Vitamin C is water-soluble among the given options.
Step 6: Important concept.
Water-soluble vitamins are not stored in the body and need regular intake.
Step 7: Final answer.
\[
\boxed{\text{Vitamin C}}
\]