for tautomerism to occur , atleast one alpha hydrogen must be acidic??

what alpha hydrogen & acidic hydrogen means here & how multiple bond on cyclocompounds reduce acidic character of hydrogen???plzzz..explain.

'x' gm of a compound A3B2C5 contains 'y' gm of A atoms

 

Using above information

Match the following 

 Dr. Ronald Lance is the greatest spell caster in the world also referred to as the most powerful saiki in the world by those who have used his powerful magic spells, weather you aiming at fixing your love, relationship or marriage, Ronald Lance is a real spells caster for your needs, bear in your mind that you are about to get in touch with our very experienced spells caster verified for casting authentic spells Call/Whats App+27634928462

Plz answer this query.....................................................................................................

how to represent the possible fischer projections for 2-bromohexane