Explanation:

- The function $y=[x+l]$ involves the greatest integer function, which means it takes the floor value of $x+l$.

- For $-4<x<-3$, the value of $[x+l]$ is constant because it rounds down to the nearest integer.

- Since the greatest integer function is constant over any open interval, its derivative is 0 in that interval.

- Specifically, at $x=-3.5$, the derivative $\frac{dy}{dx}$ is 0 because the function does not change with small changes in $x$.

Correct Answer: Option 4: 0