aying that our actual knowledge of natural laws is still imperfect and limited. （毫无疑问）
2．it is + 形容词 + to do sth / that…
1)it is obvious /evident /clear /apparent that the situation is caused directly by excessive commercial fishing. （很显然）
2)it is understandable (inevitable) that people’s attitudes are divergent on this controversial issue. （可以理解/不可避免的是）
3)it is unimaginable (incredible/unbelievable) that such a boy of 17 should have had three novels published. （难以置信的是）
4)it is imperative that something urgent be done to combat the widespread use of illegal drugs among teenagers. （…是很有必要的）
5)it is upsetting to find people who behave differently from us. we may, at first, assume that something is wrong with them. （…是令人恼火的）
6)it is impossible to concentrate if you are tense or nervous.（…是不可能的）
7)it is highly necessary for our government to stop the corruption of government officials.（某人很有必要做某事）