<p>Identify the error in these sentences.. please provide explanations. </p>
<p>A recent study of animal language (offers) provocative (theories about) the origins of such complex behaviors (as) the (colorfully and noisy) signals animals use to communicate. </p>
<p>(To stand in) Persepolis in modern Iran and look out, as Darius the First (must have done), at the immense (sweep of fields and mountains) is (to grasp) the vastness of the ancient Persian Empire. </p>
<p>The "Mayan Riviera," which (extends down) the eastern coast of Mexico, (has many hidden) caves, one (of which) is larger (than the size of) Monaco. </p>
<p>Thank you all in advance.</p>