Which of the Following Was One of the Findings in Testing

Which of the following was one of the findings in testing the principle of conservation?

A) To Piaget's surprise,four-year-old children recognized that a ball of clay rolled into a sausage shape still had the same amount of clay.
B) A five-year-old child was able to recognize that when a subordinate class of objects is placed together with a larger class of the same type of object,the whole was larger than either group.
C) Six- and seven-year-olds recognized that a ball of clay rolled into a sausage shape still had the same amount of clay.
D) Piaget found that his research worked best if he used the same types of objects and asked the same questions of all of the children that he studied.