Which of the following measurements contains 1 significant figure

connect the batteries in series and hope

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.