During an investigation into muscle strength, a group of students planned to compare their bicep muscles. Each student planned to lift a variety of masses, until they found the largest mass that they could lift. The masses were 5, 10, 15, 20 and 25 kg. The students would then plot a graph of their results.

a) Suggest how the students could improve the reliability of the investigation.

b) Suggest how the students could improve the accuracy of the investigation.

c) The teacher told the students that their investigation was too dangerous. Suggest why.