I just feel like I don't fully understand the following multiple-choice question despite the fact that I got the answer (which I still don't know if it's correct or not). 

> "An astronaut is standing on Mars. The astronaut throws and an object of mass 0.30kg vertically up at an initial speed of 9.0m/s. It reaches a maximum height of 11 metres. What is the magnitude of acceleration of the object, given the mass and radius of Mars are 6.42*10^23 kg and 3397km respectively?"
>
> A) 3.7 m^-2
>
> B) 1.4 m^-2
>
> C) 9.0 m^-2
>
> D) 9.8 m^-2

I chose A and what I did was that I calculated the force acting on the object by Mars using GMm/r^2 then I used F=ma to figure out the acceleration. However, I just feel like I did something wrong since I ignored the force acting on the object by the astronaut when he throws it up. Also I did not touch other given numbers such as the initial speed or maximum height at all.

Could someone please shed some light on this question for me please? I just began learning this topic at school hence everything seems a bit vague to me.