Answer: Elements in Group 2
Explanation: The periodic table was arranged by Dmitri Mendeleev specifically around similarites in their chemical behaviors. He found that as atomic number increases, at some point an element starts to react in a manner similar to a previous one. When that happened, he would place the larger element under the smaller one, and eventually noticed a periodicity in the table. Elements in a column (Groups) had similiar chemical properties. We know today that these similarities are due to the electron configuration, and that these configurations repeat themselves. He left gaps in the table when he could find an existing element with properties similar to others in that group. I big leap of faith, but it worked. Elements for those missing boxes were eventually discovered.
The given compound is 
Each formula unit of has 2 mol Potassium (K) atoms, 2 mol Chromium (Cr) atoms and 7 mol Oxygen (O) atoms.
Atomic weight of potassium is 39.0983 amu
Atomic weight of Chromium is 51.9961 amu
Atomic weight of Oxygen is 15.9994 amu.
Therefore the formula weight of 
= 294.1846 amu
The answer would be option B "I believe there is life on other planets." Scientific statements have a possibility to be wrong. It's not option A because option A is a opinion. It's not option C because option C is a fact. It's not option D because option D is a opinion.
Hope this helps!
Magnesium, strontium and barium are a few of the elements that have the same properties as calcium. elements found in group 2 of the periodic table have similar properties to it.
