concision problem from mgmat sc guide

problem:chap-11,page-217
the carbon emissions kilogram weight from cars is higher in summer than that of winter.
answer:chap-11,page-221
the weight of the carbon emissions from cars is higher in summer than in winter.

answer removes "that of" and other things from the Question.

If I have to compare emissions from cars vs buses , can i write like this
"the weight of the carbon emissions from cars is higher than from buses."

or I have to write like this:
"the weight of the carbon emissions from cars is higher than that from buses."

which one is right or neither of them is right? Please help.

I am having this example in mind from pronoun strategy chapter.
the money spent by her parents is less than that spent by her children. [chap-5,page 71]

Yeah, there are a couple things going on in that original sentence. I find it helps to isolate the modifiers (in parentheses) and locate (in bold) the two things that are compared.

the (carbon emissions kilogram) weight from cars is higher in summer than that of winter.

Ignoring "in summer" between "higher" and "than" for a moment, this comparison is flawed because while "weight" = "that," "from cars" is not parallel with "of winter."

Logically, "winter" and "summer" are parallel, but we don't even have parallelism between them because "of" doesn't equal "in," and the placement is screwy.

Finally, the placement of "in summer" between the comparison signal words locks us into comparing the seasons, so "that" has no place after "than."

The second one is right, and I hope the parentheses and bold I added help you see why.

I may be wrong about this, but I think the only way to make "from buses" work after the "than" is to insert "from cars" between the comparison words:

the weight of carbon emissions is higher from cars than from buses.

_________________
Emily Sledge
Instructor
ManhattanGMAT