How many different naturally-occurring common amino acids are there?

The famous scientist galileo galilei did several experiments with sloping planes, which he rolled metal balls down so that he could study motion. by changing the slope, he could study how the speed at which the ball rolled was affected. what was the independent variable in galileo's experiment? a. the speed of the ball b. the slope of the plane c. whether the ball moved d. what the ball was made of

Can anyone answer these questions? ? i need it before 1: 00pm today

When scientists are ready to publish the results of their experimentation, why is it important for them to include a description of the procedures they used?