四月份收到NATIONAL VISA CENTER的信，告知
the U.S Department of State's National Visa Center(NVC)received an approved immigrant visa petition from U.S Citizenship and Immigration(USCIS)
Due to the numerical limitations on immigrant visa issuance prescribed by law, this petition is not eligible for further processing at this time. The National Visa Center (NVC) will retain the petition until an immigrant visa becomes available. The NVC will notify the petitioner, principal applicant, or attorney of record when this petition is eligible for further processing. The principal applicant should not make any firm plans such as disposing of property, giving up jobs, or making travel arrangements at this time.