Which of the following factors determines how harmful an introduced chemical will be on the environment?
a. type of chemical
b. concentration
c. weather conditions
d. all of the above

An introduced chemical could harm the environment depeding on the type of chemical , the concentration and weather conditions, so all the above factors are equal important when it comes to what could possible harm the environment. The interaction between these factors are important as well: for example, some chemical do not react in a way that harms the environment, unless they are present in certain concentration.