16. The correct order of the following RNA polymerization/modification events is _____. 1. The polyadenylation of the pre-mRNA sequence; 2. 5'-capping 3. splicing  4. promoter clearance (A) 1-2-3-4 (B) 3-2-1-4 (C) 4-2-3-1 (D) 2-3-4-1