Which statements explain what happens at deep-ocean trenches? Check all that apply.

The given question is incomplete as the options are missing. The options related to the given question are as follows-

(A) Crust is formed

(B) Mountains are formed

(C) Seafloor spreading occurs

(D) Crust becomes molten rock

(E) Denser plates slide under lighter plates

Options (C), (D) and (E)

Explanation:

Trenches are usually defined as the V-shaped depressions that are formed in the convergent plate boundary, where the denser plate sinks below the lighter one.

These are usually extended up to a great depth, such as the the Mariana trench which is about 11 km deep. These trenches marks the boundary between the two plates.

In a convergent plate boundary, with a distinct deep oceanic trenches, the seafloor spreading takes places extensively, and the downgoing crust undergoes partial melting and becomes hot molten rocks that eventually mixes up with the magma.

Thus, the correct answers are options (C), (D) and (E).