参考答案
1） The old man always goes for a walk in that park which is near to his apartment.
句子的主从关系模糊
(有些朋友在which之前加了逗号，意思就完全不对咯，要注意。)
2） Each of the houses is painted a different colour.
主谓不一致
3） The real reason I was sleepy was that I got up early this morning.
连接词使用不当
4） He walked along the street and then suddenly realized he was lost.
中心不明白
5） The party was so dull that everyone wanted to join the one held in the apartment opposite.
句子意思表达不完整