The Civil Partnership Act 2004, introduced by the Labour

The Civil Partnership Act 2004, introduced by the Labour government and supported by the Conservative and Liberal Democrat opposition, grants civil partnerships in the United Kingdom with rights and responsibilities identical to a civil marriage.
A. introduced by the Labour government and supported by the Conservative and Liberal Democrat opposition, grants civil partnerships in the United Kingdom with rights and responsibilities identical to
B. introduced by the Labour government and supporting by the Conservative and Liberal Democrat opposition, granted civil partnerships in the United Kingdom with rights and responsibilities identical to that of
C. being introduced by the Labour government and supported by the Conservative and Liberal Democrat opposition, grants civil partnerships on the United Kingdom that has rights and responsibilities identical to those of
D. introduced by the Labour government and supported by the Conservative and Liberal Democrat opposition, grants civil partnerships in the United Kingdom with rights and responsibilities identical to those of CORRECT (correct tense (grants) and correct parallelism)
E. introduced by the Labour government and supported by the Conservative and Liberal Democrat opposition, have granted civil partnerships in the United Kingdom with rights and responsibilities identical to those of

Please explain why option E is wrong?
grants vs have granted

The Act...have. S-V error. If anything, would have to be "has granted," but even then, the perfect tense isn't required.

Can someone concisely explain when it is required to use "those of" or "that of" when performing a comparison? I'm not 100% sure when you can say X is similar to Y, or when you need to use X is similar to that of/those of Y.

X granted rights and responsibilities identical to those( plural of that) of

A - The comparison is wrong in the original sentence. 'rights and responsibilities' are compared to 'civil marriage'.
B - 'supporting by' breaks the || structure. Also 'granted' changes the tense without any reason
C - 'being introduced' is wrong because the act is already in place.
D - RIGHT. 'those' helps get the comparison right.
E - 'have granted' changes the tense without any reason

I have overlooked The S-V mismatch in the choice E. But can some one explain me would that be still wrong if it were "has granted". I am left here in the dark when I see the comments that present perfect changes the tense unnecessarily. IMO since the introduction of the law lays in the past; it does make sense for me the usage of perfect tense here, because act granted rights and it is effects are still in place today/

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