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ruminatively  adv pensativamente 
"I hope so", he said ruminatively  --espero que sí --dijo pensativo 

Collaborative Dictionary     English-Spanish
ruminatively adj. pensativamente Reverso General Dictionary 

"Collins Spanish Dictionary 8th edition published in 2005 © William Collins Sons & Co Ltd 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005"