Question

a volcano might look like an ordinary mountain. but it contains a vent, or opening, in earths crust. magma is molten rock before the crust. sometimes, the magma moves. as a result, pressure against the crust. then, hot gas, rock, and ash erupt through the vent. eruptions can kill. but they also create rich soil for farmers and millions of other people still live near vesuvius. what will happen if it erupts again? today, scientists have sensors to detect tremors inside a volcano. they can also track the

Explanation:

First Blank (the one with "before" initially):

Step1: Analyze context

The sentence is about magma in Earth's crust. The correct preposition here should show the magma's position relative to the crust. "Under" makes sense as magma is beneath the Earth's crust.

Step2: Replace the word

So we replace "before" with "under".

Second Blank (the pressure - related one):

Step1: Analyze context

Magma moving would create pressure "against" the crust. Wait, no, the structure is "pressure... against the crust" but the blank is for the verb? Wait, no, let's re - read. "Sometimes, the magma moves. As a result, pressure... against the crust." The correct verb here is "builds" (pressure builds against the crust). But maybe from the options (assuming it's a fill - in with options, but since we can infer, the logical verb is "builds" as pressure accumulates (builds up) against the crust.

Step2: Fill the blank

We put "builds" in the blank.

Third Blank (soil for...):

Step1: Analyze context

Eruptions create rich soil for "farming". Because farmers use the soil for agricultural activities, so "farming" is the appropriate word here.

Step2: Fill the blank

We replace the blank with "farming".

Answer:

First blank: under
Second blank: builds
Third blank: farming