Which of the models shown below best represents the modern understanding of the structure of the atom?

two small green balls and two small red balls labeled with plus signs are clustered at the center of a larger circle. two small yellow circles labeled with minus signs lie on the outer circle, directly across from each other.
model a

a red ball is shown, with a plus sign faintly visible on it. the ball contains 10 smaller orange balls, each labeled with a minus sign.
model b

atomic structure
model c

photos by phrood and furmanj

model a
model b

model c