Appeal from order insofar as it concerns placement unanimously dismissed and order affirmed without costs. Memorandum: Respondent appeals from an order adjudicating her a person in need of supervision and placing her in the custody of the Commissioner of Social Services (Commissioner) for a period expiring on December 21, 2000. Respondent contends that placement with the Commissioner is not an appropriate disposition; that the order fails to comply with Family Court Act § 754 (2) because it does not state the rationale for the placement; and that Family Court failed to comply with Family Court Act § 741 (a) by advising her of her right to remain silent during the dispositional hearing. All of those contentions are moot because the placement order expired on December 21, 2000 (see, Matter of Jessica MM., 256 AD2d 1027, 1028; Matter of Alex N., 255 AD2d 626, 627; Matter of Kristie II., 252 AD2d 807, 808), and this matter does not fall within the exceptions to the mootness doctrine (cf., Matter of Kevin R., 251 AD2d 1022, 1023).
Finally, respondent contends that the court violated her right to a speedy disposition pursuant to Family Court Act § 749 (b) and thus the petition should be dismissed. Because the Law Guardian did not move to dismiss the petition on that ground, that right was waived (see, Matter of Harry J., 191 AD2d 1016, 1017). (Appeal from Order of Wayne County Family Court, Kehoe, J. — Person In Need Of Supervision.) Present — Pigott, Jr., P. J., Hayes, Wisner, Scudder and Lawton, JJ.