Dave's ESL Cafe's Student Discussion Forums

[Koro]

I've come across the following sentence in the passage about vocabulary learning.

Vocabulary is, then, the most difficult part and that which takes the longerst time to learn.

I am not sure about the sentence structure after 'and'. I guess the relative pronoun which-clause modifies the antecedent 'that' (referring to the most difficult part) just before 'which'.

I'd really appreciate it if you could explain the sentence structure above.
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Koro

[pugachevV]

It says - Vocabulary is the most difficult part.
Vocabulary takes the longest time to learn.
That refers to vocabulary