3. DNA synthesis on the lagging strand in E. coli is a complex process known to involve several proteins. Initiation of a new chain is catalyzed by the enzyme (a)_________ , and elongation is catalyzed by the enzyme (b)_________ Synthesis is discontinuous, yielding short segments called (c)_________ , which are eventually joined by the enzyme (d)_________ ， which requires the cofactor (e)_________ . (5%)