Question

Consider the following ingredients used in moulding                                  

1. Dry silica sand

2. Clay

3. Phenol formaldehyde

4. Sodium silicate

Those used for shell mould casting include

(a) 1,2 and 4       (b) 2,3 and 4

(c) 1 and 3          (d) 1,2,3, and 4