选A
in的宾语在从句中做主语
主语就选what了
如果是which的话,那in which只的就是地点,也就可以用where替代,但是若替代了就a modern city has been set up where was a wasteland ten years ago 后面从句就错了
就像What I want is a ball.用what没有问题
10年前,在一片荒地建了一个现代化城市.