将下列句子合并成定语从句The man must be from Africa.It can be seen from

1.The man must be from Africa ,which can be seen from his skin.
这里it指代前面那句话,所以which代替
2.The reason why Mike refused to go to the party is that he hadn't been invited.
3.The villagers depends on the river that /which has been seriously pollutedfor their drinking water.

The man who can be seen from his skin must be from Africa. The reason why Mike refused to go to the party was that he hadn't been invited The villagers depends on the river which has been seriously polluted for their drinking water.

1.The man must be from Africa who can be seen from his skin.
2.The reason that Mike refused to go to the party was he hadn't been invited.
3.The river that the villagers depends on for their drinking water has been seriously polluted.