Question

combine the two ideas into a single sentence.
the truth was that ernesto was having trouble making new friends. he didnt want to share that fact. after all, tami seemed to be enjoying robotics.
the truth was that ernesto was having trouble making new friends, he didnt want to share that fact.
unless or
instead but

Explanation:

To combine the two ideas, we need a conjunction that shows a contrast between Ernesto having trouble making friends and not wanting to share that fact. "But" is used to introduce a contrasting idea, while "unless" (conditional), "or" (alternative), and "instead" (replacement) don't fit the contrast here.

Answer:

The truth was that Ernesto was having trouble making new friends, but he didn't want to share that fact.