20. Which of the following methods would cause competition for resources among carp and therefore help control the carp population? A. Ecologists sprout plants distasteful to carp along unvegetated river shoreline. B. Thousands of mussels are relocated from the Great Lakes to the Mississippi River. C. State officials offer free licenses to fishermen that catch more than 100 Asian carp each year. D. Conservationists build protective fences around grasses where native plankton-eating fish lay their eggs.

To determine which method would cause competition for resources among carp and help control the carp population, let's analyze each option: A. **Ecologists sprout plants distasteful to carp along unvegetated river shoreline.** - This method would not create competition among carp, as it introduces a plant that carp do not prefer. Instead, it may deter carp from the area but does not lead to competition. B. **Thousands of mussels are relocated from the Great Lakes to the Mississippi River.** - Introducing mussels could potentially create competition for food resources if carp feed on similar food sources as the mussels. However, this method primarily affects the ecosystem balance rather than directly targeting carp competition. C. **State officials offer free licenses to fishermen that catch more than 100 Asian carp each year.** - This method encourages fishing but does not create competition among carp themselves. It aims to reduce the carp population through increased fishing efforts. D. **Conservationists build protective fences around grasses where native plankton-eating fish lay their eggs.** - This method protects native fish populations but does not directly create competition among carp. It may help native species thrive but does not address carp competition. Based on this analysis, **none of the options directly create competition among carp**. However, if we consider the potential for resource competition, **option B** (relocating mussels) could lead to some competition for food resources, making it the most relevant choice in terms of creating competition among carp. Thus, the best answer is **B. Thousands of mussels are relocated from the Great Lakes to the Mississippi River.**