Question

decades after plutonium production at the hanford site in washington state left tanks of radioactive sludge near the columbia river, engineers are pumping the waste into sealed glass logs and burying them in deep vaults. the goal is not merely to store the material out of sight, but to ____ its most dangerous components so that they cannot migrate into groundwater or the wider ecosystem.
1 mark for review
which choice completes the text with the most logical and precise word or phrase?
a dilute
b recycle
c confine
d obscure

Explanation:

To solve this, we analyze each option:

• Option A: "dilute" means to make less concentrated. But the goal here is to prevent dangerous components from migrating, not to reduce their concentration. So A is incorrect.
• Option B: "recycle" means to process and reuse. The context is about storing waste to prevent migration, not reusing it. So B is incorrect.
• Option C: "confine" means to restrict or keep within limits. This fits as the goal is to keep dangerous components from migrating into groundwater or the ecosystem by restricting them.
• Option D: "obscure" means to make unclear or hidden. It doesn't relate to preventing migration of dangerous components. So D is incorrect.

Answer:

C. confine