This question tests the correct preposition for years and time expressions. When referring to years, we use the preposition 'in' because years are considered time periods we exist within. 'In 1990,' 'in the year 2000' are correct. 'At' is used for precise times (at 5 PM, at midnight). 'On' is used for specific days (on Monday, on July 4th) but not for years. For asking about birth year, 'in' is the correct preposition. Option B correctly uses 'in'.