Match the Scientists/Doctors in Column I with their discoveries of causative agents of disease from Column II.

Column I	Column II
1. Robert Koch	A. Presence of bacteria in air
2. Walter Reed	B. Yellow fever is transmitted by Aedes mosquito
3. Louis Pasteur	C. African sleeping sickness is transmitted by tsetse fly
4. David Bruce	D. Anthrax is caused by bacteria

Options:

Correct option is B

Robert Koch → D (Anthrax is caused by bacteria): Robert Koch discovered the bacterium Bacillus anthracis as the causative agent of anthrax, proving the germ theory of disease.
Walter Reed → B (Yellow fever is transmitted by Aedes mosquito): Walter Reed’s experiments demonstrated that yellow fever is transmitted by Aedes aegypti mosquitoes, a major milestone in tropical medicine.
Louis Pasteur → A (Presence of bacteria in air): Louis Pasteur disproved the theory of spontaneous generation and showed that microorganisms in the air cause fermentation and spoilage.
David Bruce → C (African sleeping sickness is transmitted by tsetse fly): David Bruce established that Trypanosoma parasites transmitted by tsetse flies cause African sleeping sickness.
Correct match: 1-D, 2-B, 3-A, 4-C → Option (b).