being a/the unprecedented siege

[NUPUR]

A) Other than the High Court, lawyers in most other B) courts have been on boycott for the last two months, C) Recently the agitation has escalated, its latest manifestation being D) a unprecedented and unfortunate siege of the High Court. E) No error

I thought error is in part A ie most of other courts, but answer is there should be the unprecedented instead of a unprecedented.

But I don't know why ?

 

[Copyright]

First of all, we would normally say "the unprecedented" – or even "an unprecedented," although "the" would be better for the specific siege we're talking about.

In this case, the error is easy to spot because "a unprecedented" is incorrect – it should be "an."

 

[NUPUR]

First of all, we would normally say "the unprecedented" – or even "an unprecedented," although "the" would be better for the specific siege we're talking about.

In this case, the error is easy to spot because "a unprecedented" is incorrect – it should be "an."

Oh yes it was really easy.
the unprecedented is wrong here, as answer is the ?

 

[Copyright]

No ... I would use "the unprecedented," although I wouldn't consider "an unprecedented" incorrect.