The blood vessel that has valves to prevent backflow is: MCQ with Answer and Explanation

Explanation:
Smooth muscle is non-striated, spindle-shaped, involuntary muscle found in the walls of hollow organs like intestines, blood vessels, uterus, and bladder. It controls peristalsis, vasoconstriction, and other autonomic functions. Skeletal muscle is voluntary and striated, cardiac muscle is striated but involuntary.

Explanation:
Louis Pasteur proved that fermentation is caused by living yeast cells, not spontaneous chemical reactions. Buchner later showed that cell-free extracts could ferment sugar, discovering enzymes. Fleming discovered penicillin, Leeuwenhoek observed microbes.

Explanation:
Minamata disease is a neurological syndrome caused by severe mercury poisoning, first discovered in Minamata, Japan, due to industrial wastewater containing methylmercury that bioaccumulated in fish. Lead causes plumbism, cadmium causes Itai-itai disease, arsenic causes arsenicosis. Mercury affects the central nervous system, causing numbness, muscle weakness, and vision problems.