egmat , could you please help me on this one!

, Why is option A wrong ?
According to my reasoning -
If we say for example -
'Bob is more handsome than Jack'It can only be interpreted in 1 way , i.e 'Bob is more handsome than Jack'
and the other way is wrong since it doesn't make sense to say -
'Bob is more handsome than Bob is more Jack'.Similarly in option A-
Balding is much more common among White males than males of other races.If we interpret -
Balding is more common among white males than males of other races are common among white males, then it doesn't make sense?
The correct interpretation is -
Balding is much more common among White males than males of other races..
(Isn't ellipses at play here? )
I suppose why option B is the correct answer is because the use of 'among' after 'than' maintains parallelism?
I don't think theres any ambiguity in the first place..
Also , when the comparison is clear, isn't repeating the helping verb/preposition optional ?
Would appreciate your help on this one!