Toms words on which our decision was ______ werent true.

A. base B. basing

C. to be based D. based

D

【解析】

试题分析：考查定语从句。汤姆的话是指我们的决定不是以正确基础上的。base on是以…为基础，which前面有介词on所以后面只用based，故选D。

考点：考查定语从句。