44.如【圖 44】所示之桁架，有關此結構之特性，下列敘述何者正確？ (A)完全拘束(completely constrained)、靜定(determinate) (B)不完全拘束(partially constrained)、靜定(determinate) (C)不正常拘束(improperly constrained)、靜不定(indeterminate) (D)完全拘束(completely constrained)、靜不定(indeterminate)