Solve this:

Q9. The co-efficient of x^k ($0\le \mathrm{k}\le \mathrm{n}$) in the expansion of E = 1 +(1+ x) + (1+x)² +......+ (1 + x)ⁿ is

        $$\begin{gathered} \left(\mathrm{A}\right){ }^{\mathrm{n}+1}{\mathrm{C}}_{\mathrm{k}+1} \left(\mathrm{B}\right){ }^{\mathrm{n}}{\mathrm{C}}_{\mathrm{k}} \\ \left(\mathrm{C}\right){ }^{\mathrm{n}+1}{\mathrm{C}}_{\mathrm{n}-\mathrm{k}-1 }\left(\mathrm{D}\right){ }^{\mathrm{n}+1}{\mathrm{C}}_{\mathrm{n}-\mathrm{k}-1} \end{gathered}$$

Q10. The last term in the binomial expansion of $\left(\sqrt[3]{2}-\frac{1}{\sqrt{2}}\right) is {\left(\frac{1}{3.\sqrt[3]{9}}\right)}^{{\log }_{3}8}$. Then the 5^th term from the beginning is 

           $$\begin{gathered} \left(\mathrm{A}\right) 4{.}^{10}{\mathrm{C}}_{6 } \left(\mathrm{B}\right) 2{.}^{10}{\mathrm{C}}_{4 } \\ \left(\mathrm{C}\right) \frac{1}{2}{.}^{10}{\mathrm{C}}_4 \left(\mathrm{C}\right){ }^{10}{\mathrm{C}}_{6 } \end{gathered}$$