If a train is slowing down it is accelerating

1. True. Acceleration can be in any direction. If the velocity and acceleration are in opposite directions the object is slowing down which is the case here.  

2. True. With the distance traveled per unit time you can calculate the velocity over each interval and by analyzing the changes in velocity find values of acceleration over time intervals. 

3. False. An object moving in circular motion is subjected to a constant centripetal force directed towards the center of the circle. Though the speed is not changing, the direction of the motion is changing since velocity is a vector and thus the acceleration affects the direction. 

4. False. Average acceleration is the change in speed divided by the time interval over which it occurs. The change in speed here is 100 km/h and it occurs over 2 hours and thus the average acceleration is 50 km/h^2.

No if a train is slowing down than the trains speed is slowing down instead of increasing 

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.