Concept:
The Mariana Trench, located in the western Pacific Ocean, is the deepest known oceanic trench on Earth.
Its deepest point is known as the Challenger Deep.
Step 1: Recall the location.
The Mariana Trench lies east of the Mariana Islands in the Pacific Ocean.
Its maximum depth is approximately
\[
11\,000\ \text{m}
\]
below sea level.
Step 2: Identify the deepest point.
The deepest location in the trench is
\[
\boxed{\text{Challenger Deep}.}
\]
Therefore, the correct option is
\[
\boxed{(A)\;\text{Challenger Deep}.}
\]