http://i66.tinypic.com/2s966o5.jpg - Question 26 why is the answer (c)..?

The diagram shows the structure of a P₄ molecule. The molecule are tetrahedral in shape, the 4 phosphorus atoms locate at the 4 corners of the tetrahedron, and each phosphorus atom are linked to the 3 neighboring phosphorus atoms. Each P-P covalent bond locates on the edge of the tetrahedral. The tetrahedron has 6 edge. This represents that there are 6 bond pairs of electrons.

...... The answer is: C. 6

Note that the tetrahedral arrangement of atoms has 6 edges; each of these represents one shared electron pair.