Four people are spaced at different distances from where a dog is barking. the barking will sound the loudest to the person who is standing

4 m away.

15 m away.

1 m away.

12 m away.

1m away, obviously is the answer

The barking will sound the loudest to the person who is standing
1 meter away.

Sounds sound louder when you're closer to the source, and softer
when you're farther away from the source.

If a lot of people are listening to the same sound, then the person who is
closest to the source will hear it the loudest, and the person farthest from
the source will hear it the softest.

If it didn't work that way, then you would not be able to hear your mother
talking to you across the table.  Her voice would be drowned out by the 
sounds of the cars in Paris, the soccer crowd at Buenos Aires, and the
crickets in the fields in Ulaanbaatar.  Life would be unbearable.

10 neutrons is the answer

Alkaline earth metals are found in group 2 of the periodic table.