2. The diagram shows an equilateral triangle, a square and a regular pentagon which all share a common vertex. What is the value of $\theta$ ?
A 98
B 102
C 106
D 110
E 112
Solution: B
The interior angles of an equilateral triangle, a square and a regular pentagon are $60^{\circ}, 90^{\circ}$ and $108^{\circ}$, respectively. Hence $\theta=360-(60+90+108)=360-258=102$.