【单选题】
设一个关系为R(A,B,C,D,E,F,G)，它的最小函数依赖集为FD={A→B,C→D,B→E,E→F}，则该关系的候选码为（ ）。
①
(A,C,G)
②
(A,C)
③
(A,E,G)
④
(A,G)
【单选题】
<imgdata-url="doc/a@6DB4CF5F9C66FD17BC71BB963B29A7B4.png"data-preview_url_ueditor="doc/a@6DB4CF5F9C66FD17BC71BB963B29A7B4.png"src="http://121.251.253.213/doc/a@6DB4CF5F9C66FD17BC71BB963B29A7B4.png/download?time=635997628381662088&token=1C6275C21B6D06966B67391CC3F19CC3&filename=png"/>
①
<imgdata-url="doc/a@F410046D7922BA32E1663874BC2B5C36.png"data-preview_url_ueditor="doc/a@F410046D7922BA32E1663874BC2B5C36.png"src="http://121.251.253.213/doc/a@F410046D7922BA32E1663874BC2B5C36.png/download?time=635997628596318465&token=777D59C04A7A8D783EA1471DFB89335B&filename=png"/>
②
<imgdata-url="doc/a@1AF2C5AB025EC26732409D751F8DD5F6.png"data-preview_url_ueditor="doc/a@1AF2C5AB025EC26732409D751F8DD5F6.png"src="http://121.251.253.213/doc/a@1AF2C5AB025EC26732409D751F8DD5F6.png/download?time=635997628730166700&token=3FB693A96149E486567C840289970469&filename=png"/>
③
<imgdata-url="doc/a@1CA14D32B72BD4002480622B3B6819F1.png"data-preview_url_ueditor="doc/a@1CA14D32B72BD4002480622B3B6819F1.png"src="http://121.251.253.213/doc/a@1CA14D32B72BD4002480622B3B6819F1.png/download?time=635997628831410878&token=E8904182AEE541F27BF648C05282E255&filename=png"/>
④
<imgdata-url="doc/a@CEF42F04E29737B84007F47A8DE4CF5D.png"data-preview_url_ueditor="doc/a@CEF42F04E29737B84007F47A8DE4CF5D.png"src="http://121.251.253.213/doc/a@CEF42F04E29737B84007F47A8DE4CF5D.png/download?time=635997628964479112&token=CF20CB3A5FB1F69385D3E2366AC1E712&filename=png"/>