Part a)
Centripetal acceleration is defined as

now here we know that


m = 3 kg
now from above formula we have


Part b)
Maximum possible tension in the string is given as

now by force equation we have



now again by above formula



I think a, im not a 100% sure tho!!!
Jogging side by side since the speed is equal and the direction is the same i.e same velocity
Answer is (c), the latent heat of fusion. That is by definition the heat that 1 kg of a substance must absorb to melt in the vicinity of its melting point.
Your weight would change but not your mass, the moon has less gravity so therefore you are going to be lighter :-)