While the use of "loose" vs "loosely" could be debated, and I don't know of a grammatical rule that prefers the use of one over the other, there are other things wrong with the sentence you can use to eliminate options. I like this sentence because it makes the test taker focus on stylistic issue while masking grammatical issues, such as:

1) Oxford comma; no need for a comma before "and" as it's not a list
2) While we're at it, no need for "and". "And" is a conjunction that introduces two separate ideas; note that "and" does not show causation. "and so" is used to show causation when only "so" would have sufficed. This creates redundancy.
3) 'B' is much cleaner and has better construction when compared to the awkward and wordy 'A' - if you absolutely must fixate on stylistic issues, construction is the safest metric you can use as it's a lot easier to get right as opposed to the "loose" v/s "loosely" debate.

(E) is wrong because "as" is used to show causation when its purpose is to introduce a new idea; "so" is a better bet. (D) makes the classic "being" mistake where the author tries to use it as a verb. Hot tip: if you can swap out "being" for "is" or "was" and the sentence still makes sense, it's probably being used incorrectly.
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You have use "loose" rather than "loosely".

Than only remaining options are B and D.
Than obiviously B looks much better than D.

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this question seems incorrect

loosely has to be used (transported is a verb)

there is a difference bew. unnecessary and not necessary (if you guys have done critical reasoning, you all will know the difference)

It's also important to look at the meaning. In D and E, the meaning changes. It says BECAUSE there were no advanced packaging facilities, the salt was sold loose. But the intended meaning is- BECAUSE salt was sold loose, there was no need for packaging facilities.

Posted from my mobile device

Definitely not a strong decision point.