Today’s ACT question of the day comes from the same science passage we saw about a week ago.
We are given a table of sediment concentrations at various depths that’s something like this:
| Depth (cm) |
Temperature (oC) |
pH | Concentration in sediment (ppm) | |||||
| SO42– | S2– | CO2 | Fe3+ | Fe2+ | O2 | |||
| 0 | 4 | 7.0 | 7.0 | 0.0 | 1.0 | 4.0 | 0.5 | 2.0 |
| 5 | 5 | 6.5 | 5.0 | 2.0 | 1.5 | 3.0 | 1.5 | 1.0 |
| 10 | 7 | 6.0 | 3.5 | 3.5 | 2.0 | 2.0 | 2.0 | 0.0 |
| 15 | 9 | 5.5 | 3.3 | 3.8 | 3.0 | 0.8 | 3.8 | 0.0 |
| 20 | 10 | 5.0 | 3.0 | 4.0 | 1.0 | 0.5 | 4.0 | 0.0 |
The test maker would like us to tell them which ion and dissolved gas will not be helpful in determining whether a sample was taken from either 15 or 20cm.
What wouldn’t be helpful? Well, if there was no data from 15 or 20cm for a given ion, or if the data was the same, those conditions would keep us from being able to differentiate between the two samples.
It turns out that O2 has one of those problems – it’s the same (0.0) at 15 and 20 cm, so it wouldn’t be able to help us understand which depth was which.
If that one was easy – great! You will need the rest of your time for other questions in the science section.
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