What would MOST probably permit a train operator to proceed with caution onto the yard lead?

A diverging route indication allows a train operator to proceed onto a yard lead with caution because it implies that the train can safely transition onto a different track or route, leading into the yard. This indication typically means that the track is prepared for the train's passage, allowing the operator to expect potential changes in speed, alignment, or other signals ahead.

The other options do not provide the necessary permission or information for moving onto the yard lead. A light signal indicating clearance, for example, typically directs movement in a straightforward manner without signaling caution, while a prohibit indication with caution explicitly restricts movement. An emergency stop recommendation is a command that halts operations entirely, further supporting that only the diverging route indication permits careful progression onto the lead.