TheancientGreeksweremuchinterestedinspeculatingonthenatureoftheworldaboutthem.

参考答案:

D

习语辨析, speculating on 表：考虑，推测；而选项人 specializing in 擅长于，专攻；B. experimenting on对进行实验；C calculating on指望着；D. pondering over沉思，深思；因此D为答案。