IIT-JEE 2011 · Paper 2, Chemistry question 7

Mechanism. Protonation of the enol-ether double bond of 3,4-dihydro-2H-pyran gives an oxocarbenium ion at C-2. The alcohol attacks it, and loss of $\ce{H+}$ gives a 2-alkoxytetrahydropyran (a THP ether).

Product type. C-2 carries two OR groups (ring O and $\ce{OCH2R}$): an acetal. This is the standard THP protection of alcohols.

(B)