The bond angle between $C-O$ and $O-H$ bonds in alcohols is close to (in $^{\circ}$)

Among the following compounds,which one can be dehydrated very easily?

Which of the following is a tertiary benzylic alcohol?

Which is the best method to prepare cycloalkene from cyclohexanol?

$(a)$ Secondary alcohol $\xrightarrow[\Delta]{H_3PO_4}$
$(b)$ Tertiary alcohol $\xrightarrow[\Delta]{H_3PO_4}$
For the above dehydration reaction,the rate of reaction will be:

The product of the reaction is: