
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
Simplify the expression $1 - \frac{1}{1 + \frac{a+1}{1 - a}}$ and identify conditions on \(a\) for it to be valid.
**A)** \(\frac{1 + a}{2} \text{ if } a \not= 1\)
**B)** \(a\) 
**C)** \(\frac{a-1}{2}\)
**D)** \(1\)
**E)** \(\frac{2}{1-a}\)

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