The correct order of priority to select functional group is:

• (A) - RCHO > RCOR
• (B) - R - O - R > R - OH
• (C) - C ≡ C > C = C
• (D) - CHO > COOH

When determining the priority of functional groups in organic chemistry, it's essential to follow specific guidelines. Here's a breakdown of the correct order based on the options provided:

Functional Group Priorities

• (A) - RCHO > RCOR: Aldehydes (RCHO) have a higher priority than ketones (RCOR).
• (B) - R - O - R > R - OH: Ethers (R - O - R) are prioritized over alcohols (R - OH).
• (C) - C ≡ C > C = C: Alkynes (C ≡ C) take precedence over alkenes (C = C).
• (D) - CHO > COOH: Carboxylic acids (COOH) actually have a higher priority than aldehydes (CHO).

Summary of Correct Order

Based on the above, the correct priorities are:

• Aldehyde (RCHO) > Ketone (RCOR)
• Ether (R - O - R) > Alcohol (R - OH)
• Alkyne (C ≡ C) > Alkene (C = C)
• Carboxylic Acid (COOH) > Aldehyde (CHO)

Thus, the correct order of priority is reflected in options (A), (B), and (C), while (D) is incorrect as carboxylic acids take precedence over aldehydes.