(a) A group of students investigated the effects of glucose and ATP on the contraction of muscle fibres. Muscle tissue was cut into pieces along the length of the muscle. These pieces were pulled apart to obtain thin strips containing muscle fibres. Fig. 1.1 shows the preparation of these thin muscle strips. [Figure 1.1] The prepared thin muscle strips were placed in a Petri dish containing Ringer's solution. Ringer's solution contains the correct balance of ions for animal tissues to function in the Petri dish. Some of these thin muscle strips were then placed on a microscope slide and their lengths were measured in mm. Ringer's solution was added to these thin muscle strips on the microscope slide and left for a few minutes. The length of each of the thin muscle strips was remeasured. This procedure was repeated with two new sets of thin muscle strips. A different solution was added to each set of thin muscle strips on a microscope slide, instead of Ringer's solution, as follows: : Ringer's solution containing glucose Ringer's solution containing ATP. The percentage decrease in length was calculated for each of the thin muscle strips. The results showed that the Ringer's solution containing ATP caused the thin muscle strips to decrease in length. Ringer's solution on its own and Ringer's solution containing glucose did not cause any change in the length of the thin muscle strips.