10 free PreACT practice questions in the real exam format, covering the official content areas, with an explanation for every answer.
PreACT Practice Test 2Tutor mode
Question 1 of 10
Science
In summer, sunlight warms the surface of a deep lake, and a layer in which temperature drops quickly with depth (the thermocline) separates warm surface water from cold bottom water. In winter, the lake is covered with ice. Scientists measured water temperature and dissolved oxygen (DO) concentration every 2 m from the surface (0 m) to the bottom (14 m) at the deepest point of the lake on July 15 and on January 15. Table 1 shows the temperatures, and Figure 1 shows the DO concentrations.
Table 1
Depth (m)
July water temperature (°C)
January water temperature (°C)
0
24
1
2
23
3
4
22
4
6
15
4
8
10
4
10
8
4
12
7
4
14
7
4
July January
According to Figure 1, on July 15 the DO concentration at a depth of 8 m was closest to which of the following?