Answer:
C
Explanation:
Both proton and neutron have a mass of 1 atomic unit. ( proton positive but neutron no charge) .
even though they both has a mass of 1 amu , they slightly differ in mass. neutron has slightly greater mass than proton .
but electrons are very smaller than protons and neutrons. electron has 1/1840 mass of proton. so they are very smaller than protons.
answer is C
