Option (B) is correct because both the assertion and the reason are true, but the reason does not fully explain the assertion. The assertion is true as the text states that microorganisms can grow over a wide range of temperatures, supported by the existence of mesophiles (20–45°C), thermophiles (40–80°C), and extreme thermophiles. The reason is also true as the text explicitly mentions that 'extreme thermophiles can tolerate temperatures above 100°C.' However, the reason is not the correct explanation because the 'wide range' of growth is due to the diversity of microbial groups (mesophiles, thermophiles, etc.), not solely due to the existence of extreme thermophiles.