41.
Your Answer is
Correct Answer is A
Explanation
sinking into... Now the participle is used as an adverbial. Item A then is an adverb, which guides the adverbial and expresses a relationship with the main clause.
B item: than comparison structure, more than should appear in pairs, wrong.
Item C: that needs a leading clause, and the following content is not a clause (no verb), wrong.
Item D: so guides the adverbial clause, wrong.