Which class of molecules contains the carbonyl group, co?

There are many compounds in organic chemistry containing carbonyl group as the part of their structure.

First kind of compounds with carbonyl group are carbonyl compounds (aldehyde with R-CHO and ketone, RCOR' as their structural formula)

Next, Carboxylic acid and their derivatives

Carboxylic acid: RCOOH

Ester: RCOOR'

Acid chloride: RCOCl

Anhydride: (RCO)2O

Amide: RCONH2

And carbohydrates, amino acids also have Carbonyl group in their structures.

Structure of carbonyl group: -C=O

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)