The correct answer is: 540 meters.
The distance between outer and home signals on a single line is 540 meters when there is advanced starter or SLB in the opposite direction. This is because the advanced starter or SLB provides a safe stopping distance for trains approaching the home signal. The distance of 540 meters is based on the assumption that the train is traveling at a speed of 40 km/h. If the train is traveling at a higher speed, the distance will need to be increased.
Option A is incorrect because it is the distance between outer and home signals on a double line. Option B is incorrect because it is the distance between outer and home signals on a single line with no advanced starter or SLB in the opposite direction. Option C is incorrect because it is the distance between outer and home signals on a single line with an advanced starter or SLB in the opposite direction, but the train is traveling at a speed of 20 km/h. Option D is incorrect because it is the distance between outer and home signals on a single line with an advanced starter or SLB in the opposite direction, but the train is traveling at a speed of 60 km/h.