Question

during the 1960s and 1970s, the population size of brown pelicans decreased severely, up to 90% in some areas. much of this decline was due to the introduction of harmful substances into the pelicans habitat— notably pesticides. in particular, the pesticide known as ddt caused pelican egg shells to thin and break before the chicks were fully developed. complete the statement. the severe decline in the brown pelican population size was mainly caused by ______. choose 1 answer: a habitat degradation b climate change c pollution d overexploitation

Explanation:

The problem is about the decline of brown pelicans due to harmful substances (pesticides like DDT) in their habitat. Pollution involves the introduction of harmful substances into the environment, which matches the cause here. Habitat degradation is more about physical damage to the habitat structure, climate change is about weather patterns, and overexploitation is about over - using or over - harvesting. So the main cause is pollution.

Answer:

C. pollution