Helen recorded the following data about the half-life of a radioisotope. Radioactive Decay of Radioisotope A Grams of Radioactive Material Remaining Time (in billions of years) 200 0 100 1 50 2 25 3 12.5 4 6.25 5 Which of the following types of graphs could Helen use to best organize her data? A. bar graph B. line graph C. histogram D. circle graph