∴△ADF is an isosceles triangle with ad = df = 9；;

AB = BE = 6，

∴cf=3；

∴, BG⊥AE, AB=6, BG= 4 in △ABG can be obtained as follows: AG=2.

And BG⊥AE,

∴AE=2AG=4，

∴△∴△abe's circumference is equal to 16,

Again? Accelerated business collection and delivery system (adopted by the United States post office)

∴△CEF∽BEA, the similarity ratio is 1: 2,

The circumference of ∴△CEF is 8.

So choose a.