Option 1: Retinol is not known as Vitamin Bj. Retinol is actually another name for Vitamin A.

Option 2: Thiamine is correct. Thiamine is also known as Vitamin Bj. It is an essential vitamin that plays a crucial role in the metabolism of carbohydrates. Its deficiency can lead to a condition called beriberi, which affects the nervous system and can cause symptoms like fatigue, muscle weakness, and nerve damage.

Option 3: Riboflavin is not known as Vitamin Bj. Riboflavin is another B vitamin, but it is commonly referred to as Vitamin B2.

Option 4: Ascorbic Acid is not known as Vitamin Bj. Ascorbic acid is actually another name for Vitamin C.

In conclusion, the correct answer is option 2, Thiamine, which is known as Vitamin Bj.