What charge would an ionized oxygen atom have?

Oxygen has 8 electrons
This means its electronic structure will be 2.6
So it has 6 electrons in its outer shell which means it needs to GAIN 2 electrons so it is stable
Once it gains the 2 electrons, it will have a charge of 2- because it has gained 2 electrons and electrons are negatively charged.

So an ionised oxygen atom will have a charge of 2-

c. It is same as the direction of the force exerted on a positive test charge.

Explanation:

Let's consider the radial electric field produced by a single point charge. We have:

1- For a positive charge, the electric field points away from the charge

2- For a negative charge, the electric field points towards the charge

Now let's put a small, positive test charge in each of these two fields. We have the following situations:

1- In the first case, the test charge will move away from the positive charge source of the field (because the force between two like charges is repulsive) --> this means that the force acting on the positive charge has same direction as the electric field

2- in the second case, the test charge will move towards the negative charge source of the field (because the force between two unlike charges is attractive) --> this means that the force acting on the positive charge has opposite direction to the electric field

So, the correct statement is

c. It is same as the direction of the force exerted on a positive test charge