The photograph shows monarch butterflies landing on plants where there are thousands of other monarch butterflies. these butterflies feed on milkweed plants as they travel south for the winter, covering distances of 5,000 km or more each year. however, the population of these butterflies has been steadily declining over the last 20 years. what is the most likely reason the population of these butterflies has been declining?

There are several reasons why the population of the monarch butterfly is facing a decline; the most most impactful one i believe to be the use of genetically modified, herbicide-resistant crops that destroy milkweed. monarch butterflies only eat milkweed, so the absence of this plant causes their death.another cause might be the urbanization of the zones where monarch butterflies are supposed to live and grow, making it difficult for them to live in such a different environment. 

The answer would be c