"either niu fen or zhang wei told on them. next morning we were summoned to the office of the school's revolutionary committee. the leaders asked us to describe what we had seen and heard."

what conclusion can be drawn from the text?

a as it is used in the passage above, the meaning of told on is "reported."
b as it is used in the passage above, the meaning of told on is "concealed."
c as it is used in the passage above, the meaning of told on is "understood."
d as it is used in the passage above