89．無線電高度表，其天線到接收機的同軸饋線 coaxial cable： (A)可調整長度‧The cable length is non-critical you can adjust and cut. (B)不可調整‧The cable length is critical you cannot cut and adjust. (C) 無關‧There are nothing to do the system. (D)以上皆非‧None above.