In the structure of 4-isopropyl-2,4,5-trimethylheptane, identify the primary, secondary, tertiary, and quarternary carbons

The classifications of the carbon as primary secondary tertiary and quaternary depends on the number of the carbon atoms attached to a carbon. In case, the carbon is attached to a single carbon, then it is referred as primary carbon. If the carbon is attached to two carbons, then it is referred as the secondary carbon, if the carbon is attached to three carbons then it is referred as tertiary, and if the  carbon forms all the bond with another carbon atom then it is referred as quatenary carbon.

The given below is the picture showing the primary, secondary, tertiary, and quarternary carbons in 4-isopropyl-2,4,5-trimethylheptane:

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.