I do not think i need to repeat myself, you are probably catching on to my feelings at this point. Hinduism is still the majority religion of modern India, thus three and four are automatically out. Buddhism was on the decline long before the arrival of the Islamic conquerors. It certainly was not a majority, so answer one is out. The destruction of former Buddhist temples by the invading Islamic armies is well known, although most had been converted to other religions anyway by this point. Remember the Islamic chroniclers would not make a distinction on just which religion these "heathen" sites belonged to. So technically, the Muslims were merely removing the evidence that at one time Buddhism was a majority religion, long after it declined. But, this is the most correct, in a frankly headache causing over simplification of a complex situation. Your teacher is a real banchod, and you can tell him or her that from me.
Edit. On second thought, do not call him or her that.