Question

the pronoun in bold is not vague. select its one clear antecedent.
have you ever played with a rubiks cube? it is a 3-d puzzle invented by ernő rubik in 1974.

Explanation:

To determine the antecedent of the pronoun "It", we analyze the context. The first sentence introduces "a Rubik's Cube", and the second sentence uses "It" to refer back to this noun. So the clear antecedent of "It" is "Rubik's Cube".

Answer:

Rubik's Cube