Which of these parts are made by powder metallurgy technique?

Question

Consider the following parts: 1. Grinding wheel 2. Brake lining 3. Self–lubricating bearings Which of these parts are made by powder metallurgy technique?            

(a) 1, 2 and 3                 (b) 2 only

(c) 2 and 3 only              (d) 1 and 2