A. The i su 10.1.0.0/23 route is a suppressed route.
B. The i su 10.1. 0.0/23 route is a summary route.
C. The i su 10.1.0.0/23 route is an IS - IS external route.
D. The R1 IS - IS router is an ASBR.
E. The R1 IS - IS router is an ABR that belongs to multiple IS - IS areas.
F. The R1 IS - IS router is performing route aggregation  and is suppressing the more specific 10.1.0.0/23 prefix.