1. The problem asks: "Taylor's dad is building a terrarium for his lizards. The number of lizards will determine how many shelves the terrarium will have. What is the independent variable?" 2. In a relationship between two variables, the independent variable is the one that you control or choose, and the dependent variable depends on it. 3. Here, the number of lizards determines the number of shelves. This means the number of lizards is the independent variable because it influences the number of shelves. 4. Therefore, the independent variable is the number of lizards. Final answer: The independent variable is the number of lizards.