複選題24. Which of the following is/are characteristic of a eukaryotic enhancer element? (A) It may be found as far as 1 to 2 kilobase from the promoter. (B) Its activity is dependent on its distance from the start site of transcription. (C) It may be positioned at the 5' end or the 3' end of the gene. (D) Its activity is dependent of its orientation. (E)It increases the level of transcription of genes under its control.