the last one is the correct answer, i took the test
In a series circuit, the current stays the same throughout the wiring and the brightness changes when adding more light bulbs. In a parallel circuit, the current changes throughout and the brightness of the light bulbs stays the same when more are added.
15+3=18km/hour Think about it like this. The boat is going 15 faster than the river, and the river is going 3 faster than the bank, so the boat is going 18 faster than the river bank
