A block of mass m₁, placed on an inclined smooth plane is connected by a light string passing over a smooth pulley to mass m₂, which moves vertically downwards as shown in the below figure. The tension in the string is

For coplanar cuncurrent and non concurrent force system, their are 3 equilibrium equation
1- algebraic sum of all horizontal force =0,
2- algebraic sum of all vertical force =0,
3- algebraic sum of all moment about any point = 0 ,
So, in this question all are correct, option (d) is correct

First find the accelaration
a = accelaration
T - m1.g.sinα = m1.a
=>T = m1(g.sinα+a)----(1)
m2.g-T=m2.a
=>T=(m2.g - m2.a)-----(2)
add the equation (1) and (2)
m1(g.sinα+a) = (m2.g - m)
=> a =(m2.g - m1g.sinα)/(m1 + m2 )
from the equation 1
T = m1(g.sinα+a)
T = m1(g.sinα+(m2.g - m1g.sinα)/(m1 + m2 ))
T = (m1.m2.g+m2.m2.g-m2.m2.g+m1.m2.g.
sinα)/(m1 + m2 )
T= m₁. m₂.g (1 + sin α)/(m₁ + m₂)

consider b = alpha

T - m1gsinb = m1*a -- Equation 1
m2g - T = m2*a -- Equation 2

Add the equations, you'll get -
m2g - m1gsinb = (m1 + m2)*a

Find a and then substitute it in equation 1 or 2. You'll get T as option D.

Pls explain the ansr.