Lake Orin is already identified by name. Choose the non-defining sentence in which the object pronoun is correctly retained.
Lake Orin, the team surveyed in June, is shrinking.
Lake Orin which the team surveyed in June is shrinking.
Lake Orin, which the team surveyed in June, is shrinking.✓Respuesta correcta
Lake Orin, that the team surveyed in June, is shrinking.
Explicación
Which is the object of surveyed and must remain because the clause is non-defining. The version that omits it is the closest distractor, but object omission is limited to defining relatives.