Create an atom with mass number equal to 3 and neutral charge. Click the red button
when done.

In order to solve the question, one must understand that:

Hence, in order to create a neutral atom with a mass number of 3, the proton and neutron number must add up to 3 while the proton and electron number must be equal.

More on mass number can be found here: link

protist eukaryotes that are not plants, animals, or fungi ("misfits")