You Are Running a Sonar Survey to Map the Bathymetry

You are running a sonar survey to map the bathymetry of an ocean basin.Using the following continuous sonar data giving the depth of the seafloor,what feature have you just discovered?
$\begin{array}{c}\begin{array}{|c|} \hline \text {Depth}\\ \text {Reading}\\ \text {Number}\\\hline 1 \\\hline 2 \\\hline 3 \\\hline 4 \\\hline 5 \\\hline 6 \\\hline 7 \\\hline 8 \\\hline 9 \\\hline 10 \\\hline 11 \\\hline 12 \\\hline 13 \\\hline 14 \\\hline 15 \\\hline 16 \\\hline 17 \\\hline 18 \\\hline 19 \\\hline 20 \\\hline\end{array}\begin{array}{c|}\hline\\\text { Depth (m) }\\\\\hline 3131 \\\hline 3101 \\\hline 3071 \\\hline 3011 \\\hline 2891 \\\hline 2846 \\\hline 2756 \\\hline 2577 \\\hline 2532 \\\hline 2487 \\\hline 2502 \\\hline 2577 \\\hline 2756 \\\hline 2921 \\\hline 3041 \\\hline 3026 \\\hline 2936 \\\hline 2756 \\\hline 2577 \\\hline 2487 \\\hline \end{array}\end{array}$

A) an abyssal plain
B) a deep trench
C) a mid-ocean ridge
D) a continental shelf