144-1 (where)

看原來子句的長相：

a world + most people are right-handed (in the world)

把+號後面的子句改成形容詞子句，用來修飾a world：
in the world 改成in which ，再一起移到前面：
a world (in which) people are right-handed
又in which = where ，於是乎答案。