Sharapova appeared to sense her opponent's (weakness) and, after having to fight for the first set, raced through the second in just 25 minutes to secure her fourth final appearance of the year.
拍照语音搜题,微信中搜索"皮皮学"使用
参考答案:
参考解析:
知识点:
皮皮学刷刷变学霸
举一反三
【单选题】电源的电动势为 E ,内阻为 r ,外电阻为 R ,要使电池有最大输出功率,则电阻 R 应等于