Select the most appropriate option to fill in the blank.

The jungle was nearly ______, so the progress was slow.

impenetrable

The most appropriate option to fill in the blank is impenetrable.

• Immaterial means not important or significant. It does not make sense in the context of the sentence because the jungle's impenetrability is important to the progress of the journey.
• Immortal means living forever. It does not make sense in the context of the sentence because the jungle is not alive.
• Immobile means unable to move. It does not make sense in the context of the sentence because the jungle is not moving.
• Impenetrable means impossible to pass through. It is the most appropriate word to fill in the blank because it describes the way that the jungle is blocking the progress of the journey.