Sentence Correction

The first decision for most tenants living in a building undergoing being converted to cooperative ownership is if to sign a no-buy pledge with the other tenants.

a) being converted to cooperative ownership is if to sign
b) being converted to cooperative ownership is whether they should be signing
c) being converted to cooperative ownership is whether or not they sign
d) conversion to cooperative ownership is if to sign
e) conversion to cooperative ownership is whether to sign

In A,B,and C, why is "being converted" wrong? I know that it is wordy and awkward. But, please be more specific.
In C, is "whether or not they sign" wrong?

OA is __E__.

Purpose : To indicate the current state of the building

The sentence has used "undergoing" for that. "being" here is redundant. We have already indicated the current state with "undergoing".

I would prefer "whether to sign or not" to "whether or not they sign"

Usually, "whether" is followed by the infinitive form of the verb.

The building is undergoing X, where X is a noun - this is why 'undergoing being converted' is incorrect. This is correctly used only in options D and E.

The proper use of 'being converted' would be:
The first decision for most tenants living in a building that is being converted to...

Secondly, 'whether' indicates both sides of the coin - something happening and it not happening. Therefore, the use of 'whether or not' is incorrect.

'Whether or not' in not idiomatic.
Eg: He wanted to know whether it's feasible.
The sentence ends there. an 'or not' doesn't follow