Answer:
the first one
Explanation: the first one because they were all on two different continents so when they seperated half of the species went on one continent and the other half went onto another one
if spring constant is doubled, the mass on spring will be doubled as well. according to this formula, F=ke
k stands for spring constant and e stands for the length extended
Sure why not I'll sub your channel
Answer:
d ≈ 320000 km
Explanation:
Echoes occurs as a result of the bouncing back of sound waves as it impinges on an obstacle. Since the echo covers two distances (i.e forth and back) the distance is written as 2d.
Velocity of radio waves is taken as the speed of light = 
time =2.15s
DISTANCE = VELOCITY *TIME
2d=vt


d= 322500000m
Distance to the moon is approximately 320000km