<em>To increase the validity of the results, all the students of Mr. Gracia's class must perform a few more experimental trials.</em>
<em>Answer: A</em>
<em>Explanation:</em>
<em>While dealing with the scientific analysis, one must always commit number of experiments to gain the most accurate and valid result. By doing number of trials, we get different approximate values that can be used to estimate the average result.</em>
<em>This average will be the nearest value of the exact answer if we add more and more number of experiments or trials. Since, the results are similar for each student in the class, they all should attempt more trials or experiments to get the most accurate result.</em>
Bacteria play an important role in decomposition of organic materials, especially in the early stages of decomposition when moisture levels are high. In the later stages of decomposition, fungi tend to dominate. Bacillus subtilis and Pseudomonas fluorescens are examples of decomposer bacteria.