The correct answer is (B) Indirect or implied reference; a casual or passing reference; an indiscreet or incidental mention of something. Also, a covert reference, a metaphor, or a parable.

Allusion comes from Latin allusio.

Examples of use:

• He made an allusion to the school's flagging work ethic during his address.
• The musician's allusion to the conductor was very complimentary.