WASHINGTON (Reuters) - Four U.S. House Republicans, including the chairman of the Energy and Commerce Committee, on Friday wrote Apple Inc chief executive Tim Cook asking him to answer questions about its disclosure that it slowed older iPhones with flagging batteries. The California-based company apologized over the issue on Dec. 28, cut battery replacement costs and said it will change its software to show users whether their phone battery is good. U.S. Senator John Thune, who chairs the Senate Commerce Committee, sent a similar letter to Apple on Tuesday. Apple did not immediately respond to a request for comment Friday.