(a) The given statement is false.
A mixture of milk and water cannot be separated by filtration as both mix well, and filtration is used to separate insoluble impurities.
(b) The given statement is false.
A mixture of powdered salt and sugar can not be separated by the process of winnowing, as both do not have any large weight difference.
(c) The given statement is false.
We do not separate sugar from tea by filtration, as sugar is completely soluble in tea, and hence, cannot be separated from tea by filtration.
(d) The given statement is false.
Grain and husk are separated with the process of winnowing, owing to their difference in weight, and not by decantation.