Final answer:
Mold was not visible on the soup before the fifth day because it grows slowly and was too small to see. Mold becomes visible as it proliferates under favorable conditions, leading to visible colonies that Soraya now observes. Therefore the correct answer is A) Mold grows slowly, so it was not visible earlier.
Step-by-step explanation:
Soraya didn't see the mold growing on the soup before the fifth day because mold grows slowly and it was not visible earlier (Option A). Mold requires time to develop to a point where it is visible to the human eye. Environmental conditions such as moisture, warmth, and nutrients are necessary for mold to become visible. In the context of biology and microbial growth, the visibility of mold over time is a clear demonstration of how microorganisms can proliferate under the right conditions, which typically include a suitable substrate like soup, stagnant air, and relatively warm temperatures. Over several days, the mold has continued to grow and reproduce, leading to the formation of visible colonies. These colonies are what Soraya now observes in the refrigerator. It is important to note that refrigeration usually slows down the growth of microorganisms, including mold, but it does not stop it entirely, especially if leftovers are stored for extended periods