Question

which relatively flat feature of the ocean floor is in the open ocean and borders the continental shelf?
abyssal plain
mid-ocean ridge
continental slope
deep-ocean trench

Explanation:

To solve this, we analyze each option:

• abyssal plain: Flat, deep - ocean floor areas in the open ocean, but not directly bordering the continental shelf.
• mid - ocean ridge: Underwater mountain range, not flat or bordering the continental shelf.
• continental slope: Steep slope between continental shelf and abyssal plain, borders the continental shelf and is in the open ocean (connecting shelf to deep ocean), and is relatively flat? Wait, no—wait, the continental slope is steep, but wait, the question is about a relatively flat feature? Wait, no, re - evaluating: The continental slope is the area that borders the continental shelf (at the shelf break) and is part of the open - ocean - adjacent ocean floor. Wait, maybe I made a mistake earlier. Wait, the options: The continental slope is the transition between shelf (shallow) and abyssal plain (deep). But the question says "relatively flat"? Wait, no, maybe the correct answer is continental slope? Wait, no, let's recall ocean floor features:

The continental shelf is a shallow, flat area. Then the continental slope is the steep drop - off, but then the continental rise (not an option) is between slope and abyssal plain. Wait, the options given:
Wait, the question is which relatively flat feature in the open ocean borders the continental shelf. Wait, maybe the continental slope is not flat. Let's re - check each option:

• Abyssal plain: Flat, but far from continental shelf (after slope and rise).
• Mid - ocean ridge: Not flat, mountainous.
• Continental slope: Steep, not flat.
• Deep - ocean trench: Deep, narrow, not flat. Wait, this can't be. Wait, maybe the question has a typo, or I misremember. Wait, no—wait, the continental slope is the area that borders the continental shelf (the shelf break is where shelf ends and slope begins). The slope is steep, but maybe the question considers it as the feature bordering the shelf in the open ocean. Wait, but the options: Let's check definitions again.

Wait, the continental slope is the steeply inclined surface extending from the shelf break (edge of continental shelf) down to the deep - ocean floor. So it borders the continental shelf (at the shelf break) and is in the open ocean (as it's beyond the shelf, in the oceanic realm). The other options: abyssal plain is flat but not bordering the shelf (separated by slope and rise), mid - ocean ridge is a ridge, deep - ocean trench is a trench. So the correct answer should be continental slope? Wait, but the question says "relatively flat"—maybe that's a mistake, or maybe I'm wrong. Wait, no, let's check standard ocean floor features: The continental slope is the feature that borders the continental shelf (at the shelf break) and is part of the open - ocean - adjacent ocean floor. So among the options, the continental slope is the one that borders the continental shelf and is in the open ocean (even though it's steep, maybe the question's "relatively flat" is incorrect, or maybe I misinterpret). Wait, no, maybe the answer is continental slope.
Wait, no, let's look up: The continental slope is the steeply sloping area between the continental shelf and the abyssal plain. It marks the boundary between the continental (shelf) and oceanic (abyssal plain) crust. So it is in the open ocean (beyond the shelf) and borders the continental shelf. The other options: abyssal plain is far from the shelf, mid - ocean ridge is in the middle of oceans, deep - ocean trench is a subduction zone feature. So the correct answer is continental slope.

Answer:

C. continental slope