Okay, yeah, the answer should be <span>D. cell → tissue → organ → system, because in the cycle system itself, the cell is a more complex organism, mainly because it does so much, as a alone or multi cell. then comes, the tissue which is also a hard working organism, because it values most of everything, like Bactria trying to come in,but its really east to damage tissue,which is my its complex, and then we have the organ which is really similar to the organ word "organism" and its really important to the system, and finally we have system, using common sense, you can't really operate with out it, so that should sum it up :) *hope this helps*
The higher the period the higher the activity of an element, therefore, since iodine is in period 6 and bromine is in period 5, the described reaction is not possible due to the fact that bromine is less active
