【1】 It is obvious that he changed his will only days before his death.

参考译文：很明显他在死前几天才改变了遗嘱。

【1】 It's the first drug that seems to have a very significant effect on this disease.

参考译文：这是第一种似乎对这种疾病有显著效果的药物。

Obvious 和significant的区别如下

【1】obvious :语气较强,指极为明显,有目共睹,非常容易看见或者明白不需要加以说明和论证。

It was obvious to everyone that the child had been badly treated.

人人一看便知，那个孩子受过虐待。

It's obvious from what she said that something is wrong.

根据她所说的，显然是出问题了。

【2】significant : 指某事由于特别优秀或有意义而显得重要或产生某种效果特别明显突出。
The results of the experiment are not statistically significant .

从统计学的观点看，实验结果意义不明显。

There are no significant differences between the two groups of students.

这两组学生没有明显差别。

Your work has shown a significant improvement.

你的工作有了显著改进。