Final answer:
Dams can improve food resources by creating opportunities for irrigation, allowing for increased agricultural productivity. This is despite the negative impacts dams have on ecosystems and biodiversity.
Step-by-step explanation:
How using a dam as a source of freshwater can also increase food resources is notably evident in the ability of dams to create irrigation opportunities (option b). By harnessing the water stored in reservoirs, dams enable the extensive distribution of water across large areas for agricultural purposes. This reliable supply can lead to enhanced agricultural productivity, ultimately contributing to a greater availability of food resources.
Moreover, while dams can displace organisms and have significant environmental impacts, they are also essential for providing continued water supplies for irrigation, urban use, hydroelectricity, and flood control. However, it is true that they cause habitat destruction, affect ecosystems, and interfere with the migration and spawning of fish, key effects that must be expertly managed to mitigate their impact on local biodiversity.