The old town has narrow streets and small houses are built close to each otherA. theyB. w

问题补充：

The old town has narrow streets and small houses are built close to each other．

A. they

B. where

C. what

D. that

答案：

A. they

B. where

C. what

(答案→)D. that

解析：考查定语从句。That are built close to each other修饰先行词narrow streets and small houses. That在句中做主语。