Answer:
Because the Earth has it's own gravity that keeps us put, and we also have the moon.
Explanation:
False, we lack cell walls whereas they have cell walls.
Answer:
A proposed answer to a s scientific problem is a hypothesis.
Answer:

negative sign indicates that the distance is decreasing with time
Explanation:
Let at any time t after noon that is 12 p.m.
distance traveled by car A = 40t
distance traveled by car B = 90-60t
then distance between the two cars at time t
............1
also, at time 1 p.m.
distance 
D=50 Km
differentiating equation 1 w.r.t. t we get

put t= 1 and D= 50 we get

