What is the best of given hashfunctions?
The question is not well-defined, since its unclear what you mean by "best". 

I suspect that the intended answer is what you said and that you are using open addressing. Then, for a given $x$, $h_2$ would eventually return all possible values in $\{0, \dots, 999\}$ (since $17$ and $1000$ are coprime). $h_1$ would only return $\frac{1000}{5} = 200$ distinct values, and $h_3$ would only return $\frac{1000}{\textrm{gcd}(32,1000)} = \frac{1000}{8}=125$ distinct values.