As the reference height is at B, so above that reference height is considered positive, and below the reference height it is considered negative. Hence the height-time graph is as such. Consider a vertical oscillating object, similar to the simple pendulum, the middle is the fastest.

Answer: Option C View the video for explanation

Answer: Option A Many have the misconception that as the astronaut and camera are floating and weightless, there is no gravitational force acting on them. Actually both are inside the gravitational field of the Earth, and there is gravitational field strength, hence there is gravitational force acting on them towards the Earth. But as together with the station, they are all ‘free falling’, hence no normal contact force on the astronaut and camera, hence give the feeling of we

Refer to the video below for the explanation. Related post: Velocity-time graph of ball released from rest with air resistance - Part 1...