The value of $$-7 \div [5 + 1 \div 2 - \left\{4 + (4  of  2 \div 4) + (4 \div 4  of  2)\right\}]$$ is:

A

$$-\frac {7}{2}$$

B

-7

C

$$\frac{7}{2}$$

D

7