Correct Answer - D
`(Q)/(At) =(K(theta_(1)-theta_(2)))/(d)`= constant
`:. K_(A)((theta_(1)=theta)/(d)) = K_(B)((theta-theta_(2))/(d))`
`(K_A)/(K_B) = (theta-theta_(2))/(theta_(1)-theta) or 3 = (theta-theta_(2))/(theta_(1)=theta)`
or, `3theta_(1)+theta_(2) = 4 theta` ...(1)
Given `theta_(1)-theta_(2) = 4 theta` ..(2)
Solving (1) and (2) we have, `theta-theta_(2)=15^(@)C`
`:. theta_(1) - theta = theta_(1)-theta_(2)+theta_(2) - theta`
`=(theta_(1)-theta_(2)) - (theta-theta_(2))`
`=20^(@)C - 15^(@)C = 5^(@)C`.