3. 例句:① This dress looks so nice.这件连衣裙看起来真漂亮。 (主系表结构)② I have to go now.我现在得走了。(主谓结构)③ I like playing the piano.我喜欢弹奏钢琴。(主谓宾结构)④ I will buy my mother a birthday present tomorrow. 明天,我要给妈妈买一份生日礼物。(主谓双宾结构)⑤ I found it difficult to learn a foreign language well.我发觉要把一门外语学好很不简单。(主谓宾补结构)