Apotassium ion (k+) would most likely bond with mg+ na+ cl- o

That would be the negative ion:  Cl-.

Cl⁻

Explanation:

A potassium ion K+ would bond with chloride ion (Cl⁻) than any other ion or element listed. Because potassium ion (K+) is electro positive and has lost an electron and having a low charge denisty while chloride ion Cl⁻ has a high charge density and is electro negative and has accepted an electron. Magnesium ion (Mg+) and sodium ion (Na+) can't bond with potassium ion (K+) because they have the same charge and has each lost an electron. Same charges or like charges repel while unlike charges or opposite charges attract towards each other.

Oxygen atom (O) can't bond with Potassium ion (K+) because oxygen is in an elemental state while potassium is in an ionic state and hence can't bond with each other. However of oxygen changes into ionic state (O²⁻), it'll definitely bond with potassium ion (K+) to form a compound (K₂O)

That would be the negative ion:  Cl-.

Explanation:

Have a good day!

It's most likely to bond with chlorine.

K⁺ has positive charge, the easiest way to form a bond is to connect to negatively charged ion. We have only one negative ion Cl⁻.
So, the answer is 
C. Cl⁻.