Which herbicide is considered selective and only targets aquatic plants?

The correct answer is Aquathol, which contains the active ingredient endothall. This herbicide is specifically designed to target aquatic plants while minimizing impacts on fish and other organisms in the environment. It works by inhibiting photosynthesis in susceptible species, effectively controlling unwanted vegetation in water bodies without affecting non-target species significantly.

Aquathol is favored in aquatic environments because of its targeted action. By focusing on specific growth patterns of aquatic plants, it maximizes efficacy while ensuring the ecological balance is maintained. This selectivity is crucial in managing aquatic ecosystems, where preserving biodiversity is essential.

In contrast, the other choices serve different purposes or have broader applications. Sodium carbonate peroxyhydrate, for instance, is more of an algaecide and is not selective for aquatic plants. Diquat is a non-selective herbicide that affects a wide range of plants, and copper chelate, while somewhat selective, can impact other aquatic organisms, including fish, depending on concentration. Therefore, Aquathol stands out for its particular ability to selectively target aquatic vegetation.