Please choose the correct answer to the question: A drinking water reservoir for a small town develops a blue-green algae bloom. The town hires a company to eliminate the problem. Which of the following should the company investigate first as a likely source of the problem?

Answer1: a pit where granite is ground up into gravel Answer2: a neighborhood where lawn chemicals are used Answer3: a junkyard where old cars are salvaged for parts Answer4: a grain elevator where corn and soybeans are stored

Answer format: answer1/answer2/answer3/answer4