
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 the universal set $U=\{-1,0,1,2,3,5\}$, set $A=\{x\in Z|x^{2}-2x-3 \lt 0\}$, and $B$ is a set consisting of natural numbers less than $4$.  
$(1)$ Find the number of subsets of $A$;  
$(2)$ Find $A\cup (\complement _{U}B)$.

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