Answer:
Zero
Explanation:
W = F × s
F = 10 N,
t = 3min = 180sec
s = 0( no change in postion)
W = 10 ×0
W = 0
The meters per second
+1t a second / 2t
2nd and only 2nd option is right
For an uniformly accelerated motion, we can write

where

is the acceleration of this motion, which in this problem is the gravitational acceleration, with a negative sign because it points downward, against the direction of the motion; h=0.540 m is the distance covered by the flea, and

is the initial velocity.
At the maximum height, the velocity is zero, so

. Therefore we can solve to find

:
You would know a decomposition reaction occurred if the reactants separated. For example from AB → A+B.
Now if you look at your options only 1 works out for that equation. Letter A.
From the compound K2CO3 it split up to K2O +CO2
It cannot be letter B because synthesis/combination occurred. The same goes for letter C. Letter D, single displacement occurred.
Again, the answer is A.