Dear everyone
This time, I would like to know the difference between "which" and "as"
used as the relative pronoun.
Both can be used when the antecedent is not a noun (phrase) but a
sentence.

Are both of each pair correct and natural? Or only one of them is natural
and correct?
Perhaps, both are wrong?

1-a. You carried the luggage yourself, which was not necessary.
1-b. You carried the luggage yourself, as was not necessary.
2-a. He is a foreigner, which is evident from his accent.
2-b. He is a foreigner, as is evident from his accent.
3-a. Her feet were bare, which was the custom in those days.
3-b. Her feet were bare, as was the custom in those days.
4-a. She has married again, which was natural.
4-b. She has married again, as was natural.
5-a. Tom was not at home, which is often the case with him.
5-b. Tom was not at home, as is often the case with him.

Would you tell me your intuition (and why).
Thank you in advance.

SIRAISI Tomio
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