sagarbuss
What is the verb in the 2nd sentence in option B. Introduction of ';' needs complete sentences on both the sides of ';'.
Doesnt the introduction of 'Though' make the sentence, a fragment?
I agree comparison in D is bad. But D is better than not having a verb as in B.
No. Introduction of 'though' does not make it a fragment. A sentence is a fragment when it lacks a main clause. Here, we have two independent clauses (the second one made subordinate to the first). Please correct me if im wrong here.
Sorry, i couldn't understand your query 'I agree comparison in D is bad. But D is better than not having a verb as in B'. I see, the second part of B is complete:-
Firstly,
... unlike statutory employees, though, independent contractors are free to.
Subject: independent contractors
Verb: are free
Am i missing anything?
Secondly,
The problem of comparison in D is not bad but its incorrect. Good enough to strike that option off

Now, lets talk about the later halves of choices B and D. We agree that both of them are (supposed to be) complete sentences that can stand on their own. Now, Lets do some meaning analysis first.
Idea presented in the 1st part:Independent contractors pay higher taxes than statutory employees and in return get lesser.
Main idea: Independent contractors are at loss and statutory employees are benefited.Idea presented in the 2nd part:Independent contractors are free to perform something that statutory employees aren't.
Main idea: Independent contractors are benefited and statutory employees are at loss. Conclusion: Both parts are present
contrasting information.
Now coming to B and D:
B
unlike statutory employees, though, independent contractors are free to perform the same type of work for multiple businessessubordinator:
Though. Though is capable of setting up contrast. Correct usage as it is showing contrast
S-V pair. Taken care of
D
in addition, unlike statutory employees, independent contractors can freely perform the same type of work for multiple businessescoordinating conjunction:
In addition. In addition is used to present similar thoughts/ideas as were presented in the earlier part of the sentence. Here, its usage is incorrect as we need to show contrast.
S-V pair: Taken care of.
Therefore B makes perfect sense and D is wrong for multiple reasons.
Please correct me if im wrong.