$${{T}_{r+1}}=C_{n}^{r}{{({{x}^{2}})}^{n-r}}{{\left( \frac{1}{{{x}^{3}}} \right)}^{r}}=C_{n}^{r}{{x}^{2}}^{n-5r}$$．令$$2n-5r=7$$，所以$$r=1$$时，$$n$$取得最小值$$6$$．选$$\text{C}$$． 
设$$n$$为正整数，二项式$${{\left( {{x}^{2}}+\frac{1}{{{x}^{3}}} \right)}^{n}}$$的展开式中含有$${{x}^{7}}$$的项，则$$n$$的最小值为（~ ）．
Options:
1: $$4$$ 
2: $$5$$ 
3: $$6$$ 
4: $$7$$ 