Self-study
Conclusion A running track with a hard surface makes for greater running speed than a soft one, at least under dry conditions, because even though step length is shorter on a hard surface, Support the time the runner's foot remains in contact with the running surface is less with a hard surface.
Summarize Argument
The author concludes that a hard track allows for faster running than a soft track, provided the conditions are dry. Why? Because on a hard track, runners spend less time with their feet touching the ground, even though their steps are shorter.
Notable Assumptions
The author assumes that runners save more time by keeping their feet off the ground than they lose by taking shorter steps on a hard track. In addition, he assumes there’s no other feature of hard tracks that allows people to run faster on them.
9.
Which one of the following, ██ █████ ██ ████████ ████ ███ ███████████ █████ █████ ██ ████ █ ███████ ████
a
Dry running conditions ███ ██ ██████████ ███ ██████ █████ █████ █████
This implies the conclusion isn’t always relevant, not that the argument is incomplete. The author restricts his statements to dry tracks only.
b
In general, taller ███████ ████ ███████ ███████ ████ ██████ ████ ███████ ███████ ███
This doesn’t say shorter runners would benefit from a softer track, because it’s possible the shorter step length allowed by the harder surface holds back runners of all heights equally.
c
Hard tracks enhance █ ████████ █████ ██ ██████ ██ ██████ ███ ███ ██████ ██ ████████ █ ███████ ████ █████████ ████ ███████████
This calls the argument into question even though it gives another reason to support the conclusion. Perhaps hard tracks make for faster running because they reduce wind resistance, not because they allow for more air time.
d
The tracks at █████ ███ ███████ ███████ ███████ █████ ████ ████ ████████ ███ ███████ ████ █████ ███ ██████ █████ ███ ███ ██ ██████████ █████
This suggests elevation is another factor that can affect running speed, but gives no difference between hard and soft tracks suggesting the reasoning is incomplete. The author does not claim that track surface is the only variable that might affect running speed.
e
To remain in ███ ██████████ █ ████ █████ ███████ ████████ █████████ ███████████ ██████████ ████ ████ █ ████ ████
This doesn’t say a soft track is any more or less likely to remain in top condition, nor what effect a track in poor condition would have on running speed.