Which of the following depends on the observer's frame of reference?a. the rest mass of a protonb. the half-life of a muonc. the length of a meterd. the passage of time

b

explanation:

c. rb

explanation:

the atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons.

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.