An aldehydic group can be protected:

Step-by-step solution

Acetals are stable in neutral and alkaline media but undergo hydrolysis in acidic media. Thus, an aldehydic group can be protected by acetal formation against alkaline oxidizing agents. Mercaptals (thioacetals) are stable in acidic media but are highly susceptible to oxidation. The sulfur atoms in mercaptals can be easily oxidized to sulfoxides or sulfones by acidic oxidizing agents. Therefore, they cannot be used to protect an aldehydic group against acidic oxidizing agents. Hence, only acetal formation is a valid