The substance that would heat up the slowest is the one with the highest specific heat. In the table provided, the specific heat values are as follows:
- Brick: 0.9
- Dry soil: 1.26
- Paper: 1.336
- Water: 4.18
Water has the highest specific heat (4.18), meaning it requires more energy to raise its temperature compared to the other substances. Therefore, the correct answer is:
water