Among the following substituted silanes the one which will give rise to cross linked silicone polymer on hydrolysis is :

The electrophile, $${E^ \oplus }$$ attacks the benzene ring to generate the intermediate $$\sigma - $$complex. Of the following, which $$\sigma - $$complex is lowest energy?

The absolute configuration of

The treatment of $$C{H_3}MgX\,\,$$ with $$C{H_3}C \equiv C - H$$ produces