Micro-economics, Indifference Curve, Properties of Indifference Curve: (1)Downward sloping to the right

Downward sloping to the right:
Indifference curve slopes downwards from left to right because when a consumer wants more units of one of the two goods, he will have to reduce the number of the units of the other good if he is to remain on the same indifference curve for keeping the same level of satisfaction.

Following statement support this property:

1: Indifference curve cannot be horizontal straight line.
2: Indifference curve cannot be vertical straight line.3: Indifference curve cannot be upward sloping.