Final answer:
The 4-letter word used for a deep shade of black in John Milton's poem "L'allegro" is Mark.
Step-by-step explanation:
The 4-letter word for a deep shade of black, which is a shortening of the name of a wood, referred to in John Milton's poem "L'allegro" is C) Mark. The line in the poem is: "And ever, against eating cares, Lap me in soft Lydian airs, Married to immortal verse, Such as the meeting soul may pierce In notes with many a winding bout Of linked sweetness long drawn out, With wanton heed and giddy cunning, The melting voice through mazes running, Untwisting all the chains that tie The hidden soul of harmony, That Orpheus' self may heave his head From golden slumber on a bed Of heaped Elysian flowers, and hear Such strains as would have won the ear Of Pluto to have quite set free His half-regained Eurydice."