The correct answer is B. Malaria was common in marshy areas where mosquitoes bred
Step-by-step explanation
An objective summary is a term used to refer to a short statement about a particular idea in an objective way, that is, it is not biased towards any opinion, interpretation, or position. According to the above, the correct answer is B. Malaria was common in swampy areas where mosquitoes breed since this sentence describes a fact clearly and objectively without deviating into personal opinions or positions.