Based on your description of the diagram, here are the correct labels for each section:
#1: Divergent Boundary - This is the boundary where two tectonic plates move away from each other.
#2: Trench - This is the feature of narrow depressions on the seafloor formed at the subduction boundary where one plate is pushed beneath another.
#3: Transform Boundary - This is where transform plates slide past each other, with little or no magma available at the plate boundary.
Feel free to let me know if you need further assistance!