Carla: I thought you ... a healthy guy!
A: were
B: are
I encountered this question on an online quiz. I choose A, but the answer key is B. I'm wondering why A is incorrect?
Carla: I thought you ... a healthy guy!
A: were
B: are
I encountered this question on an online quiz. I choose A, but the answer key is B. I'm wondering why A is incorrect?
In most cases, as user @Jason Bassford said in the comments, you will make the tenses match:
A. I thought you were a healthy guy.
X. I think you are a healthy guy.
In the context of an online quiz: as a native speaker, I would select "(A)" but there could be exceptions.
You could create a situation where "thought" was in the past tense and being a healthy guy needs to be in the present tense to show it is a continuous action.
Imagine Carla is a doctor. She is meeting with a patient Bob in the afternoon. Earlier that day, Carla met with the other doctors on her team to discuss Bob's case.
Dr. Carla says, "All the doctors met this morning to discuss your case."
Bob says, "What did they think? Am I cured?"
Dr. Carla says,
"Dr. White thought your test results are inconclusive.
"Dr. Black thought you are almost cured.
"Dr. Brown thought you are making good progress.
"I thought you are a healthy guy."
In each of these sentences, either "are" or "were" should be acceptable ---- Dr. Carla would use are if she wants to emphasize that Bob's condition is an ongoing matter (it hasn't changed from the morning until now), or "were" if she wants to emphasize what the test results were showing at that time.
English is complicated, and there are often exceptions.