organic glycol protection

https://preview.redd.it/7bdfmzw8bzmg1.png?width=1600&format=png&auto=webp&s=a770570f2223ea354170d0ba39792e40e7f71791

given andwer is C

but why not B, how to decide glycol konse C=O ko protect karega because agar ussme neeche aldehyde hota toh answer B aata