I'm curious what you think, so I'm asking. Is "they" == "Jesus and the 12" or is "they" == "the 12"?
Here's the Greek text of Mk 14.17-18 and the ESV text of same.
Καὶ ὀψίας γενομένης ἔρχεται μετὰ τῶν δώδεκα. καὶ ἀνακειμένων αὐτῶν καὶ ἐσθιόντων ὁ Ἰησοῦς εἶπεν· ἀμὴν λέγω ὑμῖν ὅτι εἷς ἐξ ὑμῶν παραδώσει με ὁ ἐσθίων μετʼ ἐμοῦ. (Mk 14:17-18, NA27)
And when it was evening, he came with the twelve. And as they were reclining at table and eating, Jesus said, “Truly, I say to you, one of you will betray me, one who is eating with me.” (Mk 14:17-18)
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