Correct Answer - B
`T=(2m_1m_2)/(m_1+m_2)g=(2xx1xx2)/(1+2)xx10N=(40)/(3)N`
If `r` is the minimum radius, then
breaking stress`=((40)/(3))/(pir^2)` or `(40)/(3pi)xx10^6=(40)/(3pir^2)`
or `r^2=(1)/(10^6)` or `r=(1)/(10^3)m`
or `r=(1)/(10^3)xx10^3m=1mm`