What is used as an antifreeze?

Acetylation reaction with acetyl chloride is carried out in the presence of which solvent?

An alcohol of formula $C_9H_{12}O$ reacts with $Na_2Cr_2O_7$ to form a compound having formula $C_9H_{10}O$. The original alcohol might be

The product formed in the following multistep reaction is:

The compound $A$ on treatment with $Na$ gives $B$,and with $PCl_{5}$ gives $C$. $B$ and $C$ react together to give diethyl ether. $A, B$ and $C$ are in the order

Which of the following can be used to test the acidic nature of ethanol?