3 Which of the following statements with regard to patent licensing under the R.O.C. Patent Act is correct?
(A) An exclusive license for a patent is not valid until it is recorded with the Specific Patent Agency.
(B) An exclusive licensee of a patent has the right to grant sub-license to a third party to exploit the licensed patent unless otherwise agreed by the parties.
(C) An exclusive licensee does not have the right to exclude the patentee from exploiting the patented invention.
(D) The sub-licensing contract granted by a non-exclusive licensee is not valid until it is recorded with the Specific Patent Agency.