Your remarks are not well grounded.

你的批注根据不足。

The class is well grounded in grammar.

这班的文法根底很好。

He is well grounded in the English language.

他的英语有很好的基础。

I doubt whether this argument is well grounded.

我怀疑这种观点是否能够站得住脚。

The rest are quote, " well rounded and well grounded".

其余三分之二则是”根基扎实、展全面”的学生。