Question

Yo investigué unos sitios por internet. Question options: Yo las investigué por internet. Yo les investigué por internet. . Yo los investigué por internet.

Answer 1

Yo los investigue por internet.
That would be the correct answer.

Answer 2

Since the word we are replacing in the sentence (sitios) is masculine, we would use a masculine pronoun to replace it.
Yo los investigué por internet.