Meiosis I just learned about this and believe
Mendel was able to attribute the variation observed in the offspring of his experiment to the controlled fertilization process.
Mendel was able to control pollination and, thus, the fertilization process in the pea plants used for his experiment.
Mendel was able to effectively predict the outcome with self-pollination or cross-pollination with different results coming from each. Thus, he logically concluded that the variation observed in the offspring of his crosses is due to the fact that he controlled the fertilization process.
More on Mendel's experiments can be found here: brainly.com/question/3186121?referrer=searchResults
The answer is concrete laundry trays.
This is because as concrete trays ages with timeit becomes coarse and rugged due to water, soap and detergents. Their smoothness gradually fades with time, thus this makes it not as good regarding to health wise standards of living.