The most important factor which contributed to the thinning of ...

[frankwu]

The most important factor which contributed to the thinning of the Martian atmosphere was probably the
 
  A) blasting of gas into space by impacts
  B) loss of the planet's protective magnetic field as it rapidly cooled
  C) chemical reactions with surface rocks
  D) formation of the polar caps

Question 2

In your own words, explain what we mean by spacetime.
 
  What will be an ideal response?

[lcapri7]

Answer to Question 1

B

Answer to Question 2

It is the combination of space and time that all observers will agree upon, even while they may disagree about space and time independently.

[frankwu]

Excellent

[juliaf]

Thanks for the timely response, appreciate it