Final answer:
Lead, with a density of 11.34 g/ml, is the only substance listed that would sink in water because its density is higher than that of water, which is 1 g/ml.
Step-by-step explanation:
In order to determine which substances would sink in water, we need to compare their density to that of water. Water has a density of 1 g/ml at room temperature. Substances with a density greater than 1 g/ml will sink in water. According to the data provided, lead has a density of 11.34 g/ml, which is much higher than the density of water, so it will sink. On the other hand, olive oil (0.92 g/ml), Styrofoam (0.03 g/ml), and balsa wood (0.1 g/ml) all have densities less than that of water, indicating these substances would float. Therefore, the only substance given that would sink in water is lead.