A 35 year old insulin dependent diabetes mellitus (IDDM) patient on Insulin for the last 10 year complains of gradually progressive painless loss of vision. Most likely he has –
Among the given options, option a & d can cause progressive painless loss of vision.

Painless loss of vision in diabeties
Gradual :- Cataract, macular edema (NPDR), Tractional retinal detachment not involving the central retina (macula) in PDR.
Sudden :- Vitreous hemorrhage (PDR), Tractional retinal detachment (PDR).
 

Now the question arises which is more common cause cataract or retinal detachment not involving the macula.
Undoubtly answer is cataract because usually retinal detachment involves central retina (macula) which causes sudden loss of vision. Retinal detachment without macular involvement is less common.
Cataract
Vitreous haemorrhage
Total rhegmatogenous retinal detachment
Tractional retinal detachment not involving the macula