To make an investigation one, should go into matters deeply, not just scratch the surface.

做调查工作不能蜻蜓点水， 要深入实际。

These problems just scratch the surface.

这些问题只是涉及到表面。

These examples just scratch the surface of the problem.

这些例子仅仅反映了问题的很少一部分。

The famine is so bad, aid can only scratch the surface.

饥荒十分严重，援助也只是杯水车薪。

We've only begun to scratch the surface of AI on the Web.

我们只是开始在网络上想象人工智能的外表。