$s_1,s_2,s_{\mathrm{3....}}$ $s_{10}$ are the speakers in a conference. If $s_1$  addresses only after $s_2$ , then the number of ways the speakers addresses is                                                                                          

• A

  _$\text{10!}$

• B

  _$\text{9!}$

• C

  _{$\text{10}\times \text{8!}$}

• D

  _{$\frac{\text{10!}}{\text{2}}$}