Look at the four squares,A ,B ,C , and D, which indicate where the following sentence could be added to the passage．Where would the sentence best fit？
For instance, when sand is poured back and forth between containers of different sizes and shapes, the quantity of sand does not change．
Piaget discovered the most widely known hallmark of the five-seven shift, an understanding of conservation, the idea that some properties stay the same despite changes in appearance．A In one of Piaget's classic experiments on the conservation of quantity, the experimenter shows children of different ages two straight rows of coins, each with six coins pressed close together, beside each other on a table．B The experimenter asks each child subject whether both rows have the same number of coins or whether one row has more．Then the experimenter spreads out the coins of one row to make the line look longer．C The child must now say whether one row has more coins．Children younger than five years old cannot understand conservation, so they invariably say that the spread-out row has more coins than the other row． D