题目2单选题
设回归模型为<img src="https://tihai-oss-cloud.itihey.com/img/3b011a04d98ecfe215b6444afe7078a7.png">,其中<img src="https://tihai-oss-cloud.itihey.com/img/7eebac194297e38dfcd00e340731db4a.png">,则<img src="https://tihai-oss-cloud.itihey.com/img/4720792ac8374ad459a2185a1758380e.png">的最有效估计量为( )A. <img src="https://tihai-oss-cloud.itihey.com/img/2222e06b116fdadfdf2338bd527f0e5e.png">B. <img src="https://tihai-oss-cloud.itihey.com/img/e1bcb823fa2007abb8d4df75bb534c76.png">C. <img src="https://tihai-oss-cloud.itihey.com/img/517f62b8f6bb56bad57f94160abdebf0.png">D. <img src="https://tihai-oss-cloud.itihey.com/img/74ead73d6d3ec2521951a8180f268241.png">