Select the option that expresses the given sentence in reported speech.

The policeman said, “It is clear that this is the work of a professional robber”.

The policeman said that it was clear that that was the work of a professional robber.

The correct option is: The policeman said that it was clear that that was the work of a professional robber.

The other options are incorrect:

• "The policeman said it was clear that is the work of a professional robber." is incorrect because the demonstrative pronoun "this" should be changed to "that" to indicate that the policeman was referring to the robbery that had already happened.
• "The policeman said that it must be clear that this was the work of a professional robber." is incorrect because the modal verb "must" is not necessary in reported speech.
• "The policeman said that it had been clearly the work of a professional robber." is incorrect because the verb tense is incorrect. The reported speech sentence should be in the past tense, not the past perfect tense.