The correct answer is C. Eichhornia crassipes, also known as water hyacinth. It is a free-floating perennial aquatic macrophyte native to the Amazon River basin in South America. It is one of the world’s most invasive species, and has been introduced to over 50 countries around the world. Water hyacinth is a serious problem in many parts of the world, where it can clog waterways, disrupt ecosystems, and harm native plants and animals. It is also a nuisance to humans, as it can block irrigation canals and water intakes, and make it difficult for boats to navigate.
Azolla is a small, free-floating fern that is native to tropical and subtropical regions around the world. It is often used as a biofertilizer in rice paddies, as it can fix nitrogen from the atmosphere. Wolffia is a tiny, free-floating duckweed that is native to freshwater habitats around the world. It is often used as a food source for fish and other aquatic animals. Trapa is a small, freshwater plant that is native to Asia, Europe, and North America. It is often used as a food source for humans and animals.
Azolla, wolffia, and trapa are all important parts of the aquatic ecosystem, but they do not cause the same problems as water hyacinth. Water hyacinth is a much larger plant that grows much faster than azolla, wolffia, or trapa. It also has a much higher reproductive rate, which means that it can quickly spread and take over an aquatic ecosystem. Water hyacinth is also much more difficult to control than azolla, wolffia, or trapa.