In Zuckerberg’s testimony before a joint session between the Senate Judiciary and Commerce committees today, the Facebook CEO was forced to confront whether his company was now effectively a monopoly.

Concerns about Facebook’s monopoly status have surfaced over the last year, with growing calls to break up the company. Sen. Lindsey Graham (R-SC) first brought up the monopoly issue; later, Sen. Dan Sullivan (R-AK) noted that regulation “can cement the dominant power,” implying that in this case, Facebook is that dominant power.

“Who’s your biggest competitor?” Graham asked Zuckerberg. The CEO struggled to answer the question, naming Google, Apple, Amazon, and Microsoft as “overlap[ing]” with Facebook in different ways.

“If I buy a Ford, and it doesn’t work well, and I don’t like it, I can buy a Chevy. If I’m upset with Facebook, what’s the equivalent product I can go sign up for?” Graham asked. When Zuckerberg attempted to again break down Facebook’s different types of services, Graham reiterated his question.

“I’m not talking about categories. I’m talking about real competition you face. ‘Cause car companies face a lot of competition. They make a defective car, it gets out in the world, people stop buying that car, they buy another one. Is there an alternative to Facebook in the private sector?”

Zuckerberg tried to give a longer answer about how the “average American uses eight different apps” to connect with their friends, attempting to frame Facebook as just one of many apps. Shortly thereafter, Graham cut to the chase and asked if Zuckerberg thought Facebook was a monopoly.

“It certainly doesn’t feel like that to me,” Zuckerberg replied, as laughter rippled through the room.

A transcript of the exchange follows below:

Sen. Lindsey Graham: Who’s your biggest competitor?

Mark Zuckerberg: Uh, senator, we have a lot of competitors.

LG: Who’s your biggest?

MZ: The categories… do you want just one? I am not sure I can give one but can I give a bunch? There are three categories that I would focus on. One are the other tech platforms: Google, Apple, Amazon, Microsoft, we overlap with them in different ways.

LG: Do they provide the same service you provide?

MZ: In different ways.

LG: Let me put it this way. If I buy a Ford, and it doesn’t work well, and I don’t like it, I can buy a Chevy. If I’m upset with Facebook, what’s the equivalent product I can go sign up for?

MZ: Well, the second category I was going to talk about…

LG: I’m not talking about categories. I’m talking about real competition you face. ‘Cause car companies face a lot of competition. They make a defective car, it gets out in the world, people stop buying that car, they buy another one. Is there an alternative to Facebook in the private sector?

MZ: The average American uses eight different apps to communicate with their friends and stay in touch with people ranging from text to email—

LG: Which is the same service you provide?

MZ: Well, we provide a number of different services.

LG: Is Twitter the same as what you do?

MZ: It overlaps with a portion of what we do.

LG: You don’t think you have a monopoly?

MZ: It certainly doesn’t feel like that to me.

[laughter]

LG: Instagram. So you bought Instagram. Why did you buy Instagram?

MZ: Because they were very talented app developers who are making good use of our platform and understood our values…

LG: Is a good business decision. My point is: one way to regulate a company is through competition, through government regulation. Here’s my question, what do we tell our constituents, given what’s happened here, why we should let you self-regulate? What would you tell people in South Carolina, given all that’s happened here, why it would be a good idea for us to let you regulate your own business practices?

MZ: … well, Senator, my position is not that there should be no regulation…. I think the internet is becoming —

LG: Do you embrace regulation?

MZ: I think the real question, as the internet becomes more important in people’s lives, is what is the right regulation —

LG: Do you as a company welcome regulation?

MZ: If it’s the right regulation, yes.

LG: Do you think the Europeans have it right?

MZ: I think that they get... things... right.

[laughter]