<span>Aldehydes and ketones have the C=O grop in their structure
Formaldehyde :
......O
......ll
......C
..../....\
..H....H</span>
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Answer: The correct option is A.
Explanation: In a chemical reaction, reactants react to form a number of products.
For the formation of products, the bonds of the individual reactants must be broken and the bonds of the products must be formed.
For example: Formation of water from hydrogen gas and oxygen gas. Reaction follows:

The Bonds of hydrogen and oxygen molecule are broken and new bonds between hydrogen and oxygen atoms are formed to give water molecule.
Answer:
1) acetylide
2) enol
3) aldehydes
4) tautomers
5) alkynes
6) Hydroboration
7) Keto
8) methyl ketones
Explanation:
Acetylide anions (R-C≡C^-) is a strong nucleophile. Being a strong nucleophile, we can use it to open up an epoxide ring by SN2 mechanism. The attack of the acetylide ion occurs from the backside of the epoxide ring. It must attack at the less substituted side of the epoxide.
Oxomercuration of alkynes and hydroboration of alkynes are similar reactions in that they both yield carbonyl compounds that often exhibit keto-enol tautomerism.
The equilibrium position may lie towards the Keto form of the compound. Usually, if terminal alkynes are used, the product of the reaction is a methyl ketone.
5 i believe the right answer