Which Grignard reagent should react with acetone to get 2-phenyl propan-2-ol?

Acetone react with Phenylmagnesium bromide to form 2-phenyl propan-2-ol. 

Conversion of tertiary butyl alcohol from tertiary butyl chloride.

6 carbon atoms of the ring form a sigma bond with the neighbouring carbon atoms of the ring. Therefore 6 sigma bonds. Another carbon atom forms a sigma bond with the carbon of -CH₃ group which in turn forms a sigma bond with each of the 3 hydrogen atoms. 4 more sigma bonds.
4 carbon atoms of the ring form a sigma bond with hydrogen atoms. 4 more sigma bonds.
-OH form 2 sigma bond.

Total =6+2+4+4 =16 sigma bonds. 

When benzaldehyde react with LiAlH₄, it form benzyl alcohol.

Fermentation is define as the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat.