LONDON (Bloomberg) — Frontline Ltd., the world's biggest oil-tanker company by capacity, ordered two crude-carrying vessels from Chinese shipbuilder Jiangsu Rongsheng Heavy Industries Group Co. Ltd.The shipping line exercised options that it acquired in June for the construction of two so-called suezmax crude carriers. The vessels will be delivered in April and June 2010, Hamilton, Bermuda-based Frontline said in a statement to the Oslo Stock Exchange yesterday.