A furniture maker wants to build a chair whose legs can move more easily across a smooth wooden floor. Based on Experiment 3, which of the following object ratings should the chair material have to best accomplish that goal?
A. 5
B. 9
C. 13
D. 19

Experiment 3
Objects can be rated according to their ability to move efficiently. The students created a scale from 5 to 30 (least to most resistant to motion due to friction) and tested four objects of a known rating. Three trials were conducted for each object, using the same methods as in Experiment 1. The results are shown in Table 3.

Experiment 1
The group of students wanted to know which materials moved down the plane in the shortest amount of time. The students used blocks of wood, steel, aluminum, glass, plastic, and concrete. The dimensions of each block were the same, the volume of each block remained constant, and the mass of the blocks was varied. The incline of the plane was set at 45◦ for each trial. The students conducted 3 trials for each material, and recorded the results in Table 1.

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Object rating 5 9 13 19 Table 3 Trial 1 1.05 1.26 1.45 1.76 Time (s) Trial 2 Trial 3 1.08 1.08 1.28 1.33 1.44 1.34 1.82 1.79 Average 1.07 1.29 1.42 1.79