Me it's the last which part of the graph depicts the motion of an object which is at rest? ( the bottom is times)straight segment acurve segment bstraight segment cstraight segment d

Its the straight segment C because its position is not going up or down, so it is not moving.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.