
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given a circle $$C: (x+ \sqrt {3})^{2}+y^{2}=16$$ and a point $$A( \sqrt {3}，0)$$, let Q be a moving point on the circle, and the perpendicular bisector of AQ intersects CQ at point M. Let the trajectory of point M be E.  
(I) Find the equation of trajectory E;  
(II) A tangent line l from point A to the circle $$x^{2}+y^{2}=1$$ intersects the trajectory E at points B and D. Find the value of |BD|.

Present the answer in LaTex format: \boxed{Your answer}
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