Alloy (1) is a mixture of many substances. Materials belonging to metals or alloys are: C (or E); Organic synthetic materials are polystyrene and plastic, so fill in: b (or d);

(2) Organic synthetic materials are polystyrene and plastics. The plastic used to make the handle is not easy to melt when heated, which belongs to thermosetting plastics.

(3) Soymilk contains some nutrients, and the nutrients that can supply human energy are: protein (or fat or sugar);

(4) Teenagers are prone to rickets due to calcium deficiency, so they choose A. 。

So the answer is:

(1)c (or e)d (or b)

(2) Thermosetting

(3) protein or fat or sugar.

(4) Answer