Learn English – Inversion – Sentence starting with rarely

subject-verb-inversion

This is from my English Cambridge Proficiency Book. In Unit 8 about inversions, I had to rewrite the sentence:

Original sentence:

It is very difficult for town centre redevelopment to achieve a harmonious balance between old and new

My answer:

Rarely is it easy for town centre redevelopment to achieve a harmonious balance between old and new

Correct question (according to the book):

Rarely do/will/can town centre redevelopments achieve a harmonious balance between old and new.

I wonder why my answer isn't acceptable.

Is there anything fundamentally wrong with my sentence?

Thanks

Best Answer

Your answer is not only perfectly acceptable, but a more accurate rendering than the one they want.

In their answer they have tacitly applied an implication (which is not even a logical implication, but a material one) that 'X is difficult' => 'X occurs rarely'. I think this is inappropriate in a grammar book.

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