“When he was alone,
Those who were around him,
Along with the twelve,
About the parables.”
Καὶ ὅτε ἐγένετο κατὰ μόνας, ἠρώτων αὐτὸν οἱ περὶ αὐτὸν σὺν τοῖς δώδεκα τὰς παραβολάς
This question to Jesus can be found in all 3 synoptic gospels, Matthew, chapter 13:10, and Luke, chapter 8:9, although the others did not make the distinction about the disciples and the 12 apostles as Mark did here. They also never mentioned that Jesus was alone. Mark said that when Jesus was alone (Καὶ ὅτε ἐγένετο κατὰ μόνας), those followers of Jesus around him (ἠρώτων αὐτὸν οἱ περὶ αὐτὸν), including the 12 apostles (σὺν τοῖς δώδεκα), asked him about the parables (τὰς παραβολάς). The disciples were confused about the use of parables.