18.AIDS is said ______ the biggest health challenge to both men and women in that area over the past few years.( )
0 138951 138959 138965 138969 138975 138977 138981 138987 138989 138995 139001 139005 139007 139011 139017 139019 139025 139029 139031 139035 139037 139041 139043 139045 139046 139047 139049 139050 139051 139053 139055 139059 139061 139065 139067 139071 139077 139079 139085 139089 139091 139095 139101 139107 139109 139115 139119 139121 139127 139131 139137 139145 151629
A. | that it is | B. | to be | ||
C. | that it has been | D. | to have been |