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Read this line from Frankenstein by Mary Shelley:
Sometimes my pulse beat so quickly and hardly that I felt the palpitation of every artery; at others, I nearly sank to the ground through languor and extreme weakness.
Which definition of languor is most likely suited for this line?

a. 14th Century: disease, distress
b. 17th Century: faintness, weariness
c. 19th Century: habitual want of energy
d. 20th Century: listless laziness