Answer: Read Explanation
Step-by-step explanation:
The "gas filled balloon" moves up, then the "upward force is larger" than the "force of gravity". The gas filled balloon causes the weight of the balloon to be heavier and hence, the force of gravity which acts on the balloon is also more than normal weight.
But in order to cause the upward motion of the balloon the upward force must overcome that weight so as to lift, therefore will be larger than the force of gravity.