Solids have:
fixed shape
o a and b
fixed size
neither a nor b

B. A and B

Explanation:

1. Solids have a definite volume, definite size and definite shape

2. The particles present in a solid are very closely packed since the intermolecular forces between them are very strong. The molecules do not move apart.

3. Melting point is the temperature at which solid changes into a liquid.

4. When a solid is heated to the melting point the intermolecular forces are overcome by the energy and the molecules present in it moves from its fixed position to take its liquid state which is called as melting.