6. The diagram shows part of a tessellation of the plane by a quadrilateral.
Khelen wants to colour each quadrilateral in the pattern so that no two quadrilaterals that meet (even at a point) have the same colour.
What is the smallest number of colours he needs?
A 3
B 4
C 5
D 6
E 7
6. B At each of the points indicated by a dot, four quadrilaterals meet, so that at least four colours are needed.
The diagram shows that four colours is possible, so the minimum number of colours Khelen needs is four.