1. the letters X and Z represent gases (carbon dioxide and oxygen ) 2. the letters w and y represent the process or cellular respiration and photosynthesis
( please explain the how do you know part too )

According to piaget, children have acquired the cognitive skill of conservation when they're able to a. understand that six ounces of liquid in a jar and six ounces in an elongated tube are equal. b. understand the viewpoint of other people. c. relate objects around them to their own needs. d. realize that the term heavy describes an object one way and the term big describes it another way. it is not b nor c. did this 2 x wrong..