विटामिन D का कौन सा रूप प्राकृतिक रूप से पर्याप्त मात्रा में नहीं पाया जाता है और सिंथेटिक (कृत्रिम) होता है?

Which of the following vitamins is responsible for blood clotting?

Water-soluble vitamins are not stored in significant amounts in the human body and need regular dietary intake. Which of the following is a water-soluble vitamin?

Fat-soluble vitamins are stored in body tissues. Which of the following is a fat-soluble vitamin?