Answer:
series
Explanation:
In a series circuit all the components are attached to one branch, so that if one component fails, all the others stop working. In a parallel circuit, however, the components are wired in separate branches, so that even if one branch fails, the rest are not disrupted.
Work is force times distance. If there's no distance, there's no work being done.
The ancient Greeks, in a theory that was suggested around 450 BC, believed that everything was from from four elements. These elements included earth, water, air and fire. Later, Aristotle supported this theory.
Therefore, the first option is correct.
Net force acting on mass = 20 - 15 = 5N. ( subtracted cuz friction always opposes the motion i.e it always acts in direction opposite to the motion of the object). According to Newton's 2nd law of motion, F(net) = ma. a =F (net) / m = 5/10 = 0.5 m/s^2. Hope it helps :)