곡면 $S= \left \{(x, y, z) \vert x ^ {2} +y ^ {2} +z ^ {2} =2, z \geq 1 \right \}$ 의 넓이는?

• ①$(4-2 \sqrt {2}) \pi$
• ②$2 \pi$
• ③$(4- \sqrt {2}) \pi$
• ④$3 \pi$
• ⑤$\displaystyle \left (4- \frac{\sqrt {2}} {2} \right) \pi$