D.
The reading between 7N and 8N would have to be 7.5N. Answers A and B are much to small and answer C is way to big.
C- Sigma Waves, This is what my teacher used to get us to remember https://www.youtube.com/watch?v=bjOGNVH3D4Y
<u>Answer</u>
The combined displacement is 2km north
<u>Explanation</u>
Since displacement is a vector quantity, we take into account the direction.
Good for us all the displacement vectors are in the same dimension, so we can make north positive and south negative or vice-versa.
We now add to obtain,

This will simplify to

Therefore the combined displacement is 2km north
Angle α between the velocity of theelectron and the magnetic field of the wire will be 90 degree