15.若x、y均为正整数,且2x•2y=128,则x+y的值为( )
| A. | 5 | B. | 6 | C. | 7 | D. | 8 |
12.一个菱形绕它的两条对角线的交点旋转,使它和原来的菱形重合,那么旋转的角度至少是( )
0 282873 282881 282887 282891 282897 282899 282903 282909 282911 282917 282923 282927 282929 282933 282939 282941 282947 282951 282953 282957 282959 282963 282965 282967 282968 282969 282971 282972 282973 282975 282977 282981 282983 282987 282989 282993 282999 283001 283007 283011 283013 283017 283023 283029 283031 283037 283041 283043 283049 283053 283059 283067 366461
| A. | 360° | B. | 270° | C. | 180° | D. | 90° |