Tom is seven years old. Pater is nine year's old.（合并为一句）Tom is ＿ ＿ younger than Pater.

根据印欧语系中“两个单词语音相近,则其语义很可能相同或者相近”的语义判断方法,英语单词mother来自于下列哪个词根?( ) A: ped B: pater C: popul D: mater