What are the consequences of altering more than one variable when conducting a scientific study

Dna is colied into chromosomes in a cell

In which of the following relationships is one organism always benefited while the other organism is always harmed

Hydrogen has only one electron in its only (and outer) electron shell. if a hydrogen atom were to absorb a small amount of energy, where would bohr say the electron would go? a. fly off the atom b. nowhere, it would just speed up. c. spiral inwards towards the nucleus d. move up to another shell that would form