7. A space lattice is a) an infinite array of points in three-dimensional Space in which each point is identically located with respect to the other b) an infinite array of points in 2-dimensional Space in which each point is identically located with respect to the other c) a limited array of points in three-dimensional Space in which cach point is identically located with respect to the other 8 . The unit's cell is obtained by a) joining the lattice points b) duplicating of lattice points c) shifting of the lattice points 28. Properties of covalent bonding are: a) Insulator or semiconductor b) High strength c) All the above 29. What matter has no fixed volume, and its volume depends on the environmental temperature and pressure. a) Liquids. b) Gas. c) All the above. 30. Two or more atoms of the same elements joined in a specific shape is called. a) Elements. b) Crystals. c) Molecules