Which of these phrases is an example of sarcasm?

A.
I'm glad my city now recycles most plastic.

B.
The notion that Earth could someday be overrun with trash is a little unsettling.

C.
It just thrills me that we have so much waste in landfills.

D.
I've heard some recycling plants create a lot of pollution.

C.

It just thrills me that we have so much waste in landfills.

The phrase that is an example of sarcasm is:

C. It just thrills me that we have so much waste in landfills.

To identify the phrase in the given options that represents sarcasm, we need to understand what sarcasm is. Sarcasm is a form of verbal irony in which someone says something that is the opposite of what they actually mean, often with a mocking or humorous tone.

Let's analyze each phrase and determine if any of them fit the definition of sarcasm:

A. "I'm glad my city now recycles most plastic."
This phrase does not appear to be sarcastic. It straightforwardly expresses that the speaker is pleased with their city recycling most plastic.

B. "The notion that Earth could someday be overrun with trash is a little unsettling."
This statement does not seem to be sarcastic either. It suggests that the idea of the Earth being overwhelmed with trash is somewhat worrisome to the speaker.

C. "It just thrills me that we have so much waste in landfills."
This phrase could be considered sarcastic. The term "thrills me" implies excitement or pleasure, which is the opposite of what one would normally feel about having a large amount of waste in landfills.

D. "I've heard some recycling plants create a lot of pollution."
This sentence does not seem sarcastic. It presents a factual statement about recycling plants potentially causing pollution.

Based on the analysis, the answer is C. "It just thrills me that we have so much waste in landfills" is an example of sarcasm because it expresses excitement or pleasure about something (having a lot of waste in landfills) that is typically undesired.

Remember, when identifying sarcasm in written or spoken language, pay attention to the tone, context, and the intended meaning behind the words.