In the selection of typical years, when more than one typical year is selected, irrigation engineering should select
选项：

A:The year when the runoff in the irrigation period is relatively dry;
B:The year when the runoff in the non-irrigation period is relatively dry;
C:The year when the dry season is longer and the runoff is dry;
D:The year when the wet season is longer, but the runoff is dry during the dry season