Billy did an investigation to learn whether bean plants will grow if they are given salt water. Billy repeated his experiment three different times. Each time, he used the same kind of been seeds, and he made the salt water by adding exactly 20 grams of salt to 1 liter of water. What is Billy doing by using the same beans and making the salt water exactly the same way each time?
A. using consistency and precision
B. making hypotheses and inferences
C. using safety and observation
D. making predictions and conclusions